Điều khiển công nghệ chế tạo và nghiên cứu các cơ chế từ giảo, từ trở, dị hướng từ vuông góc trong các màng mỏng Terfecohan

DAI HOC
QUCC
GIA
HA
NOI
TrUdng
Dai hoc Khoa hoc
TiT
nhicn

* ^
1^
^
i.

TEN DE
TAI
^ ^ - -'
OIEU KHIEN
CONG NGHE CHE TAG VA NGHIEN
CUU
CA(
CO CHE
TO
GIAG,
TO
TR6.
Dj HUONG
TU
VUONG
GOG

TRONG GAG MANG
MONG
Terfecohan
MA SO
QG.
02-06
CHUTRiDfiTAi:
PGS.TS.
NGUYIN
HOU
DLTC
HA
NO!
-
2003
^
DAI HOC QUOC GIA HA NOI
• • •
Trtrdng
Dai hoc Khoa hoc
Jxi nhien
TfiN
D^
TAI
DIEU
KHIEN CONG NGHE CHE TAG VA NGHIEN CUU CAC
• •
CO CHE TU
GIAO,
TU

TPd.
DJ
HU6NG
TD
VUONG GOC
*
TRONG CAC MANG MONG Terfecohan
MA so
QG. 02-06
PT//f^4
-J
CHUTRlDgTAl:
PGS.TS.
NGUYIN
HOU
OLTC
CAC CAN BO
PHOI
HOP
THlTC HlfiN
1.
NCS.
D6
Thi Huong Giang
2.
CN. Vu Nguyen
Thurc
3.
NCS.
Nguyen

Tlij
Minh
Hong
4.
CN.
Nguyin
Thanh Trung
5.
GS.TSKH.
Nguyin
Chau
6. TS.
LeVanVu
7.
ThS.
Chii
Due
Tiinh
8.
CN.Vu
Due
Hung
Khoa
vat
ly,
DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN

Khoa Vat ly, DHKHTN, DHQGHN
Khoa Cong nghe, DHQGHN
Khoa Cong nghe, DHQGHN
HA
NOI
-
2003
I. BAO CAO TOM TAT
1.
TflND^TAI:
"Dieu khien cong nghe che tao
vd
nghien
cihi
cdc
ccf
che
ti(
gido,
tif
trd,
di
hu&ng
tit vuong goc trong cdc mdng mong Terfecohan "
2.
MASd:
QG.02-06
3.
CHUTRID^TAI
PGS. TS. Nguyin

HSu Dire
4.
CAC CAN BO
PHOI
HOP
THUC HIEN
/. NCS. DS Thi Huang Giang
2.
CN. Vu Nguyen
Thi'fc
3.
NCS. Nguyin Thi Minh Hong
4. CN. Nguyen Thanh Trung
5. GS.TSKH. Nguyin Chdu
6.
TS.LeVdnVa
7. ThS.
ChuDifc Tiinh
8. CN.Vu
Due
Hung
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Vat ly,
DHKIH^N,
DHQGHN
Khoa Vat ly,
DHKITTN,
DHQGHN

Khoa Vat ly, DHKHTN, DHQGHN
Khoa Cong nghe Thong tin,
DHQGHN
Khoa Cong nghe Thong tin, DHQGHN
5. MUC
Tl£U
VA NOI DUNG
NGHlfiN
CUU:
5.1.
Muc tieu nghien
cihi
cua de tai
- Nghien
ciiu cc
che' vat ly, ndng cao tinh chat
tit
gido,
tvt
tra vd khd ndng ghi
tH
quang cua vat lieu
- Tim kiem cdc
I
inh chat
tilt
nun
- Che
tqo duc/c
cdc vdt lieu co khd ndng

ung
dung
- Ddo
tqo
cdn bg vd nguon
luc
khoa hoc tre
5.2.
Noi dung nghien cuu da dang ky cua de tai
-
Ngidung
1: Nghien
cicu ca
che
ti(
gido khong
IS
trong
cdc
vdt lieu
TerfecoHan co di
hu&ng tut
vuong goc
(cache
quay momen
tit)
'
Ngi
dung2:
Khdo sat tinh chat

tvt
trd cua cdc mang mong da
l&p chi(a
TerfecoHan
-
Ngi dung
3: Tang
cudng
do
l&n
cua di
htccnxg tit
vuong goc va luc khdng tit
trong cdc mdng mong TerfecoHan
6. CAC
Kl^T QUA
DAT
DirOC:
6.1.
Ket qua nghien
curu:
7.
Da che' tao thanh cong cdc mang mong tit dua tren hop chat
TerfercoHan:
cdc mang dan
l&p
TerfecoHan, da
l&p
TerfecoHanlYFe,
TerfecoHanlYFeCo

vd ba
l&p FelTerfecoHanlFe
tren thiet bi phun
xq
catot tai Trung tdm Khoa
hoc Vat lieu,
Khpa
Vat ly, Dai hoc Khoa hoc Tu nhien, Dai hoc Quoc gia Ha
Ngi.
2.
Cdc mdng mong TerfecoHan dan
l&j?
co di
hu&ng
tit vuong
g()c.
Qua trinh tit
hod trong cdc mdng mong nay la qua trinh quay momen tit tit phuang vuong
goc
v&i
mat
phdng
mdng sang phuang mat phdng mdng. Tit gido khong
16 dqt
dugc vao cd
10^
nhu'ng
bao hod
a
tit

fru'&ng
cao
(/.ijl
> 0,6 T)
/1
J.
3.
Trong cdc mdng mong ba
l&p
(sandwich) FelTerfecoHanlFe
v&i
chieu day
l&f)
Fe
(tfrj
tit 5 nm den 20
nm,
momen tit cua cdc
l&i?
Fe nam trong mat
phdng mdng nhung momen tit cua cdc l&p TerfecoHan lech ra khoi mat
phdng mdng. Cd'u
true
tit nhu
vqy
cho phep gid thiet su ton tai cua mot cau
true
domen dang
90"^
a

cdc interfaces. Do cung la nguyen nhdn lam gidm tit
truang bdo hod vd thuc day qua trinh quay xdy ra tqi tit
Iru&ng thdp
han vd
tit gido phdt trien nhanh
atittrU&ng
thdp.
Cdc mdu ba
l&p
khi u a nhiet do
T^
<250
V
(de
khit
ung sudt) cho do cam tit gido
Xxji ~
2,5xl0'-^T'^.
Gid tri nay
l&fi
han gid tri thu duac tren cdc mdng mdng
dart l&p
11].
4. Khi u
a
nhiet do
T^
>
250
V,

di
hu&ng
tit vuong goc fqi phdt trien mqnh tren
cdc mdng mong ba
hrj).
Ngodi ra
lite
khdng tit vuong goc con dqt duac
t&i
gid
^t'i
(MJ^C
^ 500
mT). Cdc thong
sdndy
thod man dieu kien ung dung cho ghi
tit vuong goc.
Ve
mat vdt
ly,
ca che luc khdng
tvt
vuong goc cao nay da duac
gidi thich bang
sU
hinh thanh
cdu
true nano trong
l&p
Fe a tren he mat. Ket

qud nay da duac khdng dinh bang cdc nghien
citu
dnh hien vi dien tu truyen
qua
11-3J.
5. Cdc ddc trung tit - dien tra tren cdc mdng da
l&p
TerfecoHanlYFe vd
TerfecoHanlYFeCo da duac khdo sdt.
Du&ng
cong tit tri R(H) cd dqng gidng
nhu
du&ng
cong tit gido
/lf//j,
tuy nhien, he so tit - dien tra
chl
dqt
cue
dqi
MR = 0,2%. Ket qud nay cho phep nhdn xet rang, cdu
hinh
tit do vuong goc
trong cdc mdng mong da
l&p
co the duac xem xet nhu la cdu hinh cua dien
trd
l&n,
Du&i tdc dung cua tit
tru&ng

ngodi, cdu
true
tit ddi thanh song song
v&i
dien tra be. Do
Id
khd ndng tiem an cua mot cdu hinh tit - dien trd
m&i.
Tuy nhien, trong cdc vat lieu dang xet, do cdc dien
tu4fc6
do
linh
dgng thdp,
nen he so tit - dien trd quan sdt duac co gid tri be. Cdc nghien citu trong cdc
vdt lieu
CO
ndng do ddt hiem thdp han la rdt cdn thiet de khang dinh gid thiet
do [4,5].
6. Cdc nghien cuu cdu
true
vi mo, tinh chdt tit, tit gido vd ca che
tie
mem trong
cdc mdng mong da
l&p
TerfecoHanlYFe vd TerfecoHanlYFeCo la mot ket
qud vuat ra ngodi khuon kho da dang ki cua de tdi nhung co y
nghia
rdt ddc
biet [6,9]. Trong cdc nghien

citu
nay, chung tdi da tqo duac trqng thdi nano
tu nhien trong cdc l&p
tut
mem cua mdng mong da
l&p
TerfecoHanlYFe vd
TerfecoHanlYFeCo. Do
Id
trqng thdi nano nhdn duac khong cdn u nhiet ma
chl cdn dieu khien thanh phdn Y. Day cung la mot cdc
tie}?
can
m&i,
mang
dam y tuang Viet Nam. Cdc vdt lieu che tqo duac cd tinh chdt tit vd tit gido
sieu mem
(fij^c =
A-?
rfiT)
vd do cam tit gido
l&n Xxu
=
29x10^
T
\ l&n
gdp
gdn 30
Ian
so

v&i
gid tri cua cdc vdt lieu
Terfenol-D
quen thugc. Cdc ket qud
da dugc mo td dua tren cdu
true
tinh the gidn doqn trong cdc
hrj? Y(Fe,Co)
16-9].
7.
Vdt lieu tit gido che tqo duac da duac
sit
dung de che tqo sensa do tit
tru&ng
dua tren hieu
itng
tit gido - dp dien. Cung voi mot bo khuyech dqi dien tich tu
che'tqo,
sensa tit gido dp dien co the
sit
dung de dd
tittrit&ng.
6.2. Cac cong
trinh
khoa hoc da cong bo:
10 cong
trinh
dd cong bd tren cdc tap chi Khoa hoc vd cdc Hoi nghi Khoa
hoc trong
nii&c

va qudc
te
7. Magnetisation process and magnetostriction in
FelTerfecohanlFe
sandwich films with perpendicular
N.H.
Due,
V.N. Thuc,
D.T.
Huong Giang, NT. Minh Hong and
N.
Chau
Physica
6327(2003)328.
2.
Magnetisation process in FelTerfecohanlFe sandwich films
D.T. Huong Giang,
N.T.
Trung and
N.H.
Due
VNU. Journal of Science, Mathematics - Physics,
2003,
dang in.
3.
Magnetisation and magnetostriction in FelTerfecohanlFe sandwich films
with an extended domain wall formation
N.H.
Due,
D.T. Huong Giang, V.N. Thuc, I. Davoli and F.

Richomme
Presented in the International Conference on Magnetism, Rome
2003,
to be
published in J. Magn. Magn. Mater., 2004
4. Spintronics dua tren tren hieu itng tit - dien tra
du&ng
ngdm vd khd ndng
irng
dung
Nguyin Hull
Due
Tuyen t$p Hoi nghi Khoa hoc va Cong nghe Nano, Ha Noi, 5/2003, tr. 48.
5.
Dieu khien cdu
trdc
vi mo vd cdu
true
tit cua cdc mdng mong co cdu
trdc
nano nhdn tqo dqng
l&p
ddt hiem - kim
loqi
chuyen tiep
Nguyen HOii Dire
Se in trong: Tuyen tap Hoi
nghi
Vdt ly Chdt ran todn qudc
Idn tint

IV,
Niii
Coc
5-7/11/2003.
6. Nanostructure and magnetic softness of magnetostrictive
TerfecohanlYFeCo multilayers
D.T. Huong Giang,
N.H.
Due,
F.
Richommer and
S.
Schulze
J. Magn. Magn. Mater., 262 (2003) 361.
7.
Nanostructure and magnetic softness of magnetostrictive
{TerfecohanlYFeCo} multilayers
D.T. Huong Giang,
N.H.
Due,
F.
Richommer,
N.T.
Hien and
S.
Schulze
Proceedings of The Sixth German - Vietnamese Seminar on Physics and
Engineering, Chemnitz, Germany, 25 May - 31 May,
2003.
8. Vdt lieu tit gido kieu spring - magnet TerfecohanlYFeCo

D6 Thi
Hircng
Giang,
Nguyin Hun
Dire,
Vu Nguyen
ThiJc
Se in trong: Tuyen tap Hoi nghi Vdt ly Chdt ran todn qudc
Ian tint
IV,
Niii
Coc
5-7/11/2003.
9. Natural nanostructure and magnetization reversal process in
TbFeColYJFeCo)j.j,
spring - magnets type multilayers
N.H.
Due, D.T. Huong Giang and
N.
Chau
Presented at the International Symposium on Advanced Magnetic Technology,
Taipei
2003,
to be published in J. Magn. Magn. Mater., 2004.
10.
Sensa do tit
tru&ng
dua tren hieu
itng
tit gido - dp dien

Nguyin Thi Minh Hong, D6 Thi
Huofng
Giang, Vu Nguyen
Thiic,
Chu
Diic
Trinh, Vu
Dure
Hirng,
Nguyin
Hun Du-c
Se in trong: Tuyen tap Hoi nghi Vat ly Chdt ran todn qudc
Idn
thit
IV,
Niii
Coc
5-7/11/2003.
6.3.
Ket qua dao tao:
6.3
J.
Tien sy: 01
-
DdThi
Huang Giang (dang thuc hien)
6.3.2. Thqc sy: 01
-
Vil Nguyen
Thitc (dang thuc hien)

6.3.3.
Cii
nhdn: 06
-
va
Nguyen Thitc Khoa Vdt ly, DHKHTN, DHQGHN
Nguyen
Thanh Hdi
Nguyen Thi Minh Hong
Nguyen
Thanh Trung
Dqng Thi Minh Hong
va
Ditc Hung
Khoa Vdt ly, DHKHTN, DHQGHN
Khoa Vdt ly, DHKHTN, DHQGHN
Khoa Vdt ly, DHKHTN, DHQGHN
Khoa Vat ly, DHKHTN, DHQGHN
Khoa Cong nghe, DHQGH
6.3.4.
Sinh vien nghien
cihi
khoa hoc:
Da
hiring dan
05 sinh vien nghien cuu khoa hoc, trong do:
-
01
sinh vien dqt gidi nhi cap Bo GD&DT nam 2002
-

01
sinh vien dqt gidi ba cap
TrU&ng
Dqi hgc Khoa hgc Tu nhien nam
2003
1.
TINH HINH THANH QUYET TOAN
KINH
PHI:
Tong kinh
phi
duac cap: 60 trieu dong
- Nam
2001:
45 trieu dong
Dd nhdn vd quyet todn day
du.
-
Nam 2002: 15 trieu dong
Dd nhdn vd quyet todn day du.
XAC NHAN CUA BAN CHU
NHIEM
KHOA
K
TS. Nguyen The
Binh
Ha Ngi,
ngdy
30 thdng 11 nam 2003
CHU TRI DE TAI

PGS.TS. Nguyin
HUu Dice
XAC NHAN CUA
TRUING
IL
SUMMARY OF THE REPORT
1.
TITLE OF THE PROJECT:
''Control
preparation technologies and study mechanisms of magnetostriction,
magnetoresistance and perpendicular anisotropy in TerfecoHan - based
films'*
2.
CODE OF THE PROJECT:
QG. 02-06
3.
DIRECTOR OF THE PROJECT:
Assoc.
Prof.
Dr. Nguyen Huu
Due
4.
PARTICIPANTS IN THE PROJECT:
7.
PhD. Student Do Thi Huong Giang
2.
BSc. Vu
Nguyen
Thuc
3.

PhD. Student Nguyen Thi Minh Hong
4. BSc. Nguyen Thanh Trung
5.
Prof.
Dr. Nguyen Chau
6.
Dr.LeVanVu
7.
MSc. Chu
Due
Trinh
8. BSc. Vu
Due
Hung
5. OBJECTIVES AND CONTENTS:
5.1.
Objectives:
- To study physical mechanisms, improve magnetostrictive and
magfietoresistive
properties and magneto-optical recording potential of
materials
- To investigate novel magnetic properties
- To prepare materials with high application potentials
- To train young scientist resources
Departement of Physics,
HUS,
VNU
Departement of Physics, HUS, VNU
Departement of Physics, HUS, VNU
Departement of Physics, HUS, VNU

Departement of Physics, HUS, VNU
Departement of Physics, HUS, VNU
Faculty of Technology, VNU
Faculty of Technology, VNU
8
5.2.
Contents:
- Study mechanism of giant magnetostriction in TerfecoHan-based films
with perpendicular anisotropy
- Study magnetoresistive properties of multilayer thin films based on
TerfecoHan
- Improve the strength of anisotropy and coercivity force in
TerfecoHan-based films
6.
OBTAINED
RERULTS:
6.1.
Scientific results :
7.
Magnetic films based on TerfecoHan compound consisting of TerfecoHan
single layer films, multilayer TerfecoHanlYFe and TerfecoHanlYFeCo films
and three-layer (sandwich)
FelTerfecoHanlFe
films have been successfully
prepared by using RF-magnetron sputtering machine in Center of Materials
Science, Department of Physics, Hanoi College of Science, VNU.
2.
Single layer TerfecoHan films exhibit a perpendicular anisotropy. The
magnetisation process in these thin films can be described by the rotation of
magnetic moments from

out-of-plane
into the film plane direction.
Magnetostriction reaches a giant value of about
10'\
However, the
saturation magnetic field is still high
fuj^^
> 0,6 T [1].
3.
Studies carried out in the three-layer (sandwich) FelTerfecoHanlFe films
have shown that for films in which the
Fe-layer
thickness
(tfj
ranges from 5
nm to 20 nm, magnetic moments in the
Fe-layers
orient in the film plane
whereas those in the
TerfecoIIan-layers
orient out of the film plane. Such
magnetic structure generates 90
^-domain
walls at interfaces. This leads to
the decreasing of saturation magnetic and promotes remarkably the rotation
process of magnetic moments at low fields. After annealing at temperature
T^
< 250
X'
(in

order
to release stress induced in the preparation), the
magnetostrictive susceptibility
Xxii ^
2,5xlO'^T^
has been obtained in these
sandwiches. This value is larger than that of single layer TerfecoHan films
HI.
4. The perpendicular anisotropy has been developed significantly in these
three-layer FelTerfecoHanlFe films after annealed at temperature
T^
> 250
TT.
In addition, the perpendicular coercivity force reached to a value as
large as 500 mT. These investigated films with perpendicular anisotropy and
high coercivity are very promising for perpendicular magnetic recording
materials. The mechanism of high perpendicular coercivity has been
explained by the nanostructural formation of the upper Fe-layer. These
results have been verified by studies in transmission electron microscope
images.
5. The magnetoresistance effects in mutilayer thin films TerfecoHanlYFe and
TerfecoHanlYFeCo have been investigated. These films exhibit a
magnetoresistance ratio MR of 0,2% only. It can be supposed that the
perpendicular magnetization configuration in these mutilayers supports a
large resistance state. In applied magnetic fields, the change into parallel
magnetization configuration leads to a small resistance state. Thus, it is able
to propose a new magnetoresistance configuration. The low MR value
observed in the investigated multilayers results from low polarisation of
electrons 4f Further studies in materials with lower concentration of rare
earth will he necessary to confirm this proposal [4,5].

6. Studies in the microstructure, magnetic and magnetostrictive properties and
softness mechanism in mutilayer thin films TerfecoHanlYFe and
TerfecoHanlYFeCo is somewhat out of the scope of this project. However,
the obtained results have a great significance. The nanostructure of soft
layers has been naturally formed in as-deposited multilayers
TerfecoHanlYFe and TerfecoHanlYFeCo by controlling
Y-concentration.
This opens
a
novel original approach to prepare natural nanocrystalline
state. These multilayers exhibit an exellence magnetic softness
(He
= 0,3 mT)
and exellence magnetostrictive softness with extremely high magnetostrictive
10
susceptibility
Xx -
13x10'^
T'\
which is thirty times larger than that of well-
known
Terfenol-D.
The
se
suits have been discussed in terms of the
discontinuous crystalline configuration in soft layers [4,5].
7.
The prepared materials have been used for application in magnetic field
sensor based oh
magnetostrictive-piezoelectric

effects. Combining with a
home-made electronic amplifier, sensor can be used for detecting magnetic
fields.
6.2. Publications :
7.
Magnetisation process and magnetostriction in FelTerfecohanlFe
sandwich films with perpendicular
N.H.
Due,
V.N. Thuc, D.T. Huong Giang,
N.T.
Minh Hong and N.
Qiau
Physica B327 (2003) 328.
2.
Magnetisation process in FelTerfecohanlFe sandwich films
D.T. Huong Giang,
N.T.
Tmng and
N.H.
Due
VNU. Joumal of Science, Mathematics - Physics,
2003.
3.
Magnetisation and magnetostriction in FelTerfecohanlFe sandwich films
with an extended domain wall formation
N.H.
Due,
D.T. Huong Giang, V.N.
Tliuc,

I. Davoli and
F.
Richomme,
J. Magn. Magn. Mater., 2004, in press.
4. Spintronics dua tren tren hieu ung
ti(
- dien trd
du&ng
ngdm vd khd ndng
ling dung
Nguyin Hull
Due
Tuyen tap Hoi nghi Khoa hoc va Cong nghe Nano, Ha Noi, 5/2003, tr. 48.
5. Dieu khien cdu
true
vi mo vd cdu
true tie
cua cdc mdng mong co cdu true
nano nhdn tqo dqng lop ddt hiem - kim loqi chuyen tiep
Nguyin
HfiiiDirc
Se in trong: Tuyen tap Hoi nghi Vat ly Chdt ran todn qudc
Idn
thu
I\\
Nui
Coc
5-7/11/2003.
11
6. Nanostructure and magnetic softness of magnetostrictive

TerfecohanlYFeCo multilayers
D.T.
Huong Giang,
N.H.
Due,
F.
Richommer and
S.
Schulze
J. Magn. Magn. Mater., 262 (2003) 361.
7.
Nanostructure and magnetic softness of magnetostrictive
{TerfecohanlYFeCo} multilayers
D.T. Huong Giang,
N.H.
Due,
F.
Richommer,
N.T.
Hien and
S.
Schulze
Proceedings of The Sixth German - Vietnamese Seminar on Physics and
Engineering, Chemnitz, Germany, 25 May - 31 May,
2003.
8. Vat lieu
ti(
gido kieu spring - magnet TerfecohanlYFeCo
D6 Thi Huang Giang, Nguyin Huu
Dire,

Vu Nguyen
Thiic
Se in trong: Tuyen tap Hoi nghi Vdt ly Chdt ran todn qudc
Idn thi(
N,
Niii
C6c
5-7/11/2003.
9. Natural nanostructure and magnetization reversal process in
TbFeColYJFeCo)f,,
spring - magnets type multilayers
N.H.
Due, D.T. Huong Giang and
N.
Chau
J. Magn. Magn. Mater., 2004, in press.
10. Sensa do
tic tru&ng
dua tren hieu
itng tit
gido - dp dien
Nguyin Thi Minh H6ng, D6
Tlii Huofng
Giang, Vu Nguyen
Tliiic,
Qiu Due
Trinh, Vu
D^Q
Hung, Nguyin Huu
Due

Se in trong: Tuyen tap Hoi
nghi Vdt
ly Chdt ran todn qudc
Idn thit
IV,
Nui
Coc
5-7/11/2003.
6.3.
Training results :
6.3.1.
PhD:
01
- Do Thi Huong Giang (in progress)
6.3.2.
Master: 01
- Vu Nguyen Thuc (in progress)
6.3.3. Bachelor: 06
12
- Vu Nguyen Thuc Departement of Physics, HUS, VNU
- Nguyen Thanh Hai Departement of Physics, HUS,
VNU
- Nguyen Thi Minh Hong Departement of Physics, HUS,
\ ^NU
- Nguyen Thanh Trung Departement of Physics,
HUS,
VNU
- Dang Thi Minh Hong Departement of Physics, HUS,
\ 'NU
- Vu Due Hung Faculty of Technology, VNU

6.3.4.
Student^s
Scientific Research Projects:
05 students presented their contributions at the Student's Scientific
Confetences
- 01 student was awarded The Second Prize of Ministry of Education and
Training in the academic year 2002
- 01 student was awarded The Third Prize of University of Natural Science
in the academic year 2003
13
• ^
III.
BAO
CAO
MUC LUC
I Trang
1.
Lcri
mo
d^u
15
2.
Noi dung va ket qua nghien curu
2.1.
Cdc
phuang
phdp
thuc nghiem 17
2.2.
Cdc ket qud nghien

citu
18
3.
Ketlu$n
23
Tai lieu tham khao 26
Phuluc
27
Phi^'u ddng
ky ket qua
nghien
curu
1.
LOI
MO DAU
vat
lieu
tir
giao (cung nhu cac vat lieu ap dien khac) la cac vat lieu co kha
nang bien doi dien nang thanh ca nang.
Chiing thudng
duac su dung de che tao cac
cam bien, bo phan truyen dong, bo phan dich chuyen cung nhu cac thiet bi dien-ca
khac.
Trong s6 cac vat
li6u
tir giao dang duac nghien curu hien nay, vat lieu
tijf
giao
dang mang mong dang gay duac su quan tarn

chii
5^
dac
bi6t
do
kich thudfc
ciia
chiing
thich
hap cho viec ung dung trong cac thiet bi vi ca. Cac vat
lieu
nay con ket
hgp
duac nhieu uu diem khac nhu nang
luang loi
ra
Idn,
tan so boat dong cao va co
the dieu
khi^n dugfc
i\x
xa
[1-3].
De tang
cuofng
hieu qua
ling
dung
ciia
cac thiet bi

sir
dung
hieu ling tijr
giao, cac mang mong phai co iii giao cao trong viing
tijr truofng
tha'p,
tiic
la do cam
tir
giao
Idn (xx = dX[d{[ioH)
>
2x10^
T')
va
lire
khang
t\x
nho
(MOHC
« 100 mT) [4]. Cac cd gang lam giam
tir trucfng
dieu khien doi vai cac vat
lidu tijr
giao da duac
tie'n
hanh theo
nhilu each
khac nhau. Theo
truyin

thO'ng,
cac
nghiSn
cuu
vl
vat lieu
tir
giao
diu
dua tren cac hop kim
TbFcj
va
(Tb,Dy)Fe2 tiic
la
Terfenol va
Terfenol-D
(Ter la Tb, fe la Fe, D la Dy va
noi
la ten phong
thi
nghiem
nal tim
ra hap kim nay). Di
hu6ng tiir cQng
co
thd
giam bang
each sir
dung vat lieu a
trang thai vo

djnh
hinh.
Tuy nhien, trong trang thai nay, cac hap chat
a-Terfenol
va
a-Terfenol-D
co
ca'u triic
speri
tir,
trong do momen
tir ciia
Tb phan bd trong mot goc
con rong.
Chinh
dieu nay lam giam nhiet do Curie
(Tc =
410 K v6i hop kim
v6
dinh
hinh
a-Terfenol) va do do lam giam
tir
giao
d
nhiet do phong.
Cung
vdi
muc
dich

tang cudng gia tri
tir
giao trong
viing
tir trudng
thS^p,
cac
hap chat
a-TbCo2
(TercoNeel) (Neel
la ten phong
thi
nghiem nai nghien cuu
hgp
cha't
nay) da dugc khao sat. O trang thai tinh the, cac hgp chat
TbCoj
cd nhiet do
Curie tha'p ban nhiet do phdng
(Tc
= 230 K) do Co cd thuoc
tinh
tir gia
bin
[4]. Khi
chuyen sang trang thai v6 dinh
hinh,
mac dii
ca'u triic
speri tir van

tdn
tai nhu da
quan sat
tha'y
ddi vdi cac hgp kim
a-TerfenoI,
nhung
vi
tir
tinh
cua phan mang Co
dugc tang cudng (do hieu
ling
the
tfch) nen
nhiet do Curie da tang
len
gan 600 K [1].
Nguyen nhan ca ban lam giam tir giao cua cac hgp chat
a-TbFe2
va
a-TbCoj
so
vdi cac hgp kim tinh the la do ca'u triic speri tir
ctia
phan mang
daft
hiem. De tang tir
giao trong cac hgp chat nay can phai giam gdc con cua cac momen tir trong phan
15

mang
da't
hi^m.
Dieu nay da dugc thuc hien trong cac hgp chat a-Tb(Fe,Co). Cudng
dd tuang tac trao d6i
3<i-4/trong
cac hgp
ch^t
a-TbFe, a-TbCo va a-Tb(Fe,Co) la
gdn
nhu nhau nhung momen tir ciia phan mang (Fe,Co) trong cac hgp chat
a-Tb(Fe,Co)
Idn
han ban momen tir cua Fe va Co trong cac hgp
chSft
a-TbFe va a-TbCo tuang ung
[5-7].
Dilu
nay cd the lam tang nhiet dp Curie va lam giam ca'u triic gdc cua cac
momen trong phan mang
da^t
hiem. Ngoai ra, phuang phap thay the' Co cho Fe cdn
cho phep che' tao dugc ra cac hgp chat giau nong dp Tb han va do 66 by vpng se lam
tang ca tir giao
ISn
dp cam tir giao trong viing tir trudng
thA'p
d nhiet dp phdng.
Tie'p tuc phat buy uu the cua Co va
d^

lam giam anh hudng
ciia
Dy, cac hgp
chat vd dinh
hinh
cd ndng dp Tb cao ban
la
a-Tb(Feo,5sCO()45),
5 (tii'c
la TerfecoHan)
da dugc che tao
vji
nghien cuu thanh cong tai bo
mdn
Vat ly Nhiet dp tha'p bdi nhdm
tac gia Nguyin
Hun Due
va cac cong
sir
[8,9].
6
day, Ter cd
nghla
la
Tb,/^
la Fe,
CO
la Co va Han la ten viet tat ciia Ha Noi. Cac hgp
ch^t
nay hien nay van dang

giir
ky luc the' gidi vl tir gao dang mang mong A
= 1080x10 \
Cac mang mdng dan
Idp
la cac he ddng nha't. Ddi vdi
tinh
cha't tir giao, thanh
phdn
da't hie'm va kim
loai
chuyen tiep dugc chpn trong hgp chdt TerfecoHan da cho
sir
tdi uu vl nhiet dp Curie va gia tri tir giao bao
ho^.
D^
dat dugc tir giao
Idn
ban d
tir trudng tha'p, cdn phai lam giam tir trudng bao boa
/V^s-
Cd
nhilu phuang phap
de'
thuc hien dugc dilu nay va mot trong sd dd la viec che tao cac mang mdng da
Idp
bao gdm cac Idp cd tir giao cao (TeFeCo) va cac
Idp
tu
mim

cd dp tir hoa
Idn
(FeCo)
thudng dugc quan tam [10-12]. Y tudng nay
hinh
thanh tir mdi lien he giua tir dp
bao hoa
Ms
va tir trudng bao boa
H^.
Thay
vi
giam hang sd di hudng
K^
(=
/jJ4^^)
nhu cac
each
tiep
can
trudc day, su to hgp nay
vdn
dam bao vat lieu cd tir giao
Idn
ddng thdi giam dugc tir trudng bao hoa
H^
do dp tir boa trung
blnh
M^
dugc tang

cudng. Xet theo ca che dao tir, cac mdm dao tir (nucleations) cd the
hinh
thanh mot
each dl
dang trong cac Idp vat lieu tir
mIm
va sau dd se
Ian
truyin (propagate) sang
cac
Idp
vat lieu tir giao, cd di hudng tir
Idn
ban [10,13]. Do cac mdm dao tir va ca
qua trinh dao tir thudng
xudt
phat tir
bl
mat cua vat lieu ndi chung va
bl
mat ciia cac
hat tinh the ndi rieng nen
Idp
tir
mIm
cd cdu triic nano tinh
th^
se thuan
Igi
ban

nhieu cho cac qua trinh dao tir so vdi cdu triic dong nha't (tinh the hoac vd dinh
16
hinh).
Dd
la
cdu
hinh
tdi uu cho cac vat lieu tir to hgp de nang cao dac
tinh
tir mem
ciia cac vat lieu tir to hgp. Theo truyin thdng, cdu triic
nand
dang hat thudng dugc
hinh thanh tir trang
thai
vd dinh
hinh
ban ddu nhd cac qua trinh
xir
ly nhiet [5]. Cac
nghien
cihi
cua Quandt va cac ddng nghiep da
chi
ra rang, trang thai nano cd the
hinh
thanh
mdt each
tu nhien trong
Idp

tir
mIm
ngay sau khi che tao (khdng cdn
xir
ly nhiet) khi pha tap B, Si, Cu vd Nb
[2,14].
Tuy nhien ban che' ciia phuang phap nay
la tir giao giam do ddng gdp tir giao
am
ciia pha tinh the. Trong dl tai nay, cdu triic
nano dugc dilu khien bang viec pha tap Y vao (FeCo). Vdi mot ndng dp tdi ban, cdu
triic nano
ciia Idp
tir
mIm
Y(Fe,Co) se nhan dugc mot each tu nhien ngay sau khi
che'
tao. Cac ket qua nghien
ciiu
cdu triic, cac
tinh
chdt tir, tir giao, tir - dien trd va
anh hudng ciia qua trinh ii nhiet den cac
tinh
chdt ciia cac mang mdng da
Idp
TerfecoHan/Y(FeCo) da dugc tap trung nghien cuu.
Cung dua tren y tudng che' tao vat lieu to hgp kieu spring-magnet nay, de dan
gian boa cong nghe che tao ma vdn cho dugc tfnh chdt tir
mIm

va tir gao cao, dap
ling yeu cdu ung dung, cac mang ba
Idp
(sandwich) Fe/TerfecoHan/Fe vdi sd chu ky
nhd cung da dugc
che
tao va nghien cuu. Qua trinh tir boa va ca che
hinh
thanh vach
dd men cung da dugc thao
luan.
.
' '•)
2.
NOI DUNG vA
K£T
QUA
NGHII&N
CUU
2.1.
Cac phuang phap
thirc
nghiem
Cac he mang mdng da
Idp
Terfecoban/Yj^Fe,.^
va
Terfecohan/Yx(Fen,7Coo,3)i.x
{x = 0; 0,1 va 0,2) cd so chu ki n = 50 vdi
chilu

day cac
Idp
tir giao Terfecohan
^TbFcCo
= 12 nm va cac
Idp
tir
mIm
Y(FeCo)
fyp^co
= 10 nm va cac mang ba
Idp
Fe/TerfecoHan/Fe vdi chilu day
Idp
TerfecoHan khong doi
^rbFeCo
= 600 nm va
chilu day cac
Idp
Fe thay ddi tir
/p^
= 5 nm den 90 nm da dugc che tao bang phuang
phap
phiin
xa catdt tai Trung tam Khoa hpc Vat lieu, Trudng Dai hpc Khoa bpc Tu
nhien, Dai hpc Qudc gia Ha Noi.
Cac mdu sau khi che tao dugc
ii
nhiet trong dilu kien chan khdng cao
5x10"^

mbar, thdi gian
Ih
tai cac nhiet do khac nhau tai Bp mdn Vat ly Nhiet dd Thdp,
Khoa vat ly, Trudng Dai hpc Khoa hpc Tu Nhien.
17
Cdu triic vi mo
ciia
mdu dugc xac dinh thdng qua phep do
phd
nhilu xa tia X
tai Bp mdn Vat ly Ghat
rdn,
Khoa Vat ly, Dai hpc Khoa hpc Tu nhien va anh chup
hi^n
vi dien tir truyin qua dp phan giai cao (HR-TEM) tai Trudng Dai hpc Tong hpp
Chemnitz, CHLB Due.
Cac
tinh
chdt tir
ciia
mdu dugc khao sat bang phep do dudng cong tir
tri
tren he
do tir ke mdu rung (VSM) dugc thuc hien tai Trung tam Khoa hpc Vat lieu, Trudng
Dai hpc Khoa hpc Tu nhien va Trung tam
ITIMS,
Trudng Dai hpc Bach khoa Ha
Ndi.
Cac nghien
ciiu tinh

chdt tir giao ciia mdu dugc thuc hien thdng qua phep do tir
giao bang phuang phap quang hpc tai Bp mdn Vat ly Nhiet do Thdp, Khoa Vat ly,
Trudng Dai hpc Khoa hpc Tu Nhien.
2.2.
Ket qua nghien curu
2.2.a.
Mdng dan
l&p
TerfecoHan
Cac mang mdng TerfecoHan dan Idp vdi
dd
day t
-
500 nm da dugc che tao va
nghien
ciiu.
Cac nghien
ciiu
vl
tinh
chat tir va tir giao da chi ra
rdng
mang ngay sau
khi che' tao the hien di hudng tir vuong gdc. Qua trinh tir hoa trong cac mang mdng
nay la qua trinh quay
hidmen
tir tir phuang vuong gdc vdi mat phang mang sang
phuang mat phang mang. Tir giao khdng
Id
dat dugc

Idn
A
= 1080x10 "^
nhung bao
hoa d tir trudng cao
JL/^H
> 0,6
T (xem hinh 1) [1]. Gia tri tir
giao dat dugc vdn giu ky luc
Idn
nha't so vdi cac ket qua dat
dugc tren cac vat lieu tir giao
dang mang dugc nghien
cioi
tren the' gidi cho den nay. Cac
mang sau khi
ii
nhiet, di hudng
tir chuyen tir phuang vuong gdc
sang phuang song song vdi mat
phang mang. Qua trinh u nhiet
cd tac dung
khir
ung sudt va
1200
1000
800
o
^
600

400
200
-
0.2
0.0 0.2
^^
H
(T)
0.4 0.6
Hinh I.
Dudng cong
su
pint
thugc rita
tir gido
vao
tir
trudng tren cdc mang don
Idp TerfecoHan
18
^
0
: so
_—^
w
'
•
1
-1
tang cudng

tinh
tir
mIm
tren cdc mang nghien
ciiii
(xem phu luc kem theo).
2.2.b.
Mdng ba
Idp
(sandwich) FelTerfecoHanlFe
Cac mang mdng 3
Idp
(sandwich)
Fe/TerfecoHan/Fe vdi chilu day
Idp
Fe thay
doi
/pe
= 5, 10, 15, 20, 25, 40, 60 va 90 nm
(ki
hieu S5,
SIO,
S20, S25, S40, S60 va S90
tuang ling) da
dude
che' tao. Cac nghien
ciiu
vl cdu triic vi md,
tinh
chdt tir va tir giao da

dugc tie'n hanh tren cac mdu. Trong cac vat
lieu loai nay,
tinh
chdt tir phu thupc manh
vao dd day
Idp
Fe. Vdi chilu day
Idp
Fe
(rpj
tir 5 nm de'n 20 nm, momen tir cua cac
Idp
Fe
nam trong mat phang mang nhung momen tir
cua cac
Idp
TerfecoHan lech ra khoi mat
phang mang (xem hinh 2). Cdu triic tir nhu
vay cho phep gia thiet su tdn tai
ciia
mdt cdu
yx^
(T)
triic ddmen dang 90° d cac interfaces. Dd
Hinh
2. Dudng cong tit tri do theo
cung la nguyen nhan lam giam
lii'
trudng bao
^'"'^"^ ^'^"^ ^^^"^ ^"^''' ^"^"^ ^^' ^-^^

^ ^ , , , ciia cdc mang
ba
Idp FelTerfecohanlFe
hoa va thuc day qua trinh quay xay ra
tai
tu
ngay sau khi che tqo
trudng thdp ban va
lii
giao phat trien nhanh d
tir trudng thdp. Cac mdu ba
Idp
khi u d nhiet
dd
T^A
^
250
°C
(de khir
ling
sudt) cho
dp cam tir giao
j^//
'^
2,5xlO^T'.
Gia tri nay
Idn
ban gia tri thu dugc tren cac mang
mdng dan Idp
[1].

Di hudng tir vuong gdc vdi
H^
tang len den gan 500 mT cd the dat dugc tren
cac mdu vdi chilu day
t^^=
10 nm sau khi dugc
ii
d nhiet dp cao cho phep vat lieu
cd kha nang
ling
dung de lam cac vat lieu ghi tir vuong gdc. Trong khi dd,
sir
ket hgp
giira Idp
Terfecohan vdi cac
Idp
Fe cd
tinh
tir
mIm
khi dp day
Idp
Fe
Idn
(> 30 nm)
khi
ii
d nhiet dp cao
ihi
di hudng tir vuong gdc se bi pha va va di hudng tir mat

phang nhanh chdng dugc thiet lap.
Sir
khac nhau vl dp Idn
ciia lire
khang tir
giija
cac
lap trong trudng hgp nay ddn den qua trinh dao tir khac nhau trong cac
Idp
va do dd
19
ddn den su
hinh
thanh cdu triic ddmen dang 180° trong viing chuyen tiep.
Sir
hinh
thanh vach ddmen trong viing chuyen tie'p giua cac Idp vat lieu gay
nen
cac
tinh
chdt
tir va tir giao
Ii
thii.
Cac ket qua dua tren nhtrng phep do tir dp va tir giao se cho phep
nhan biet mdt
each
gian tiep su xudt hien cua vach ddmen tren cac he mang mdng
ba
Idp

nay. Cac ket qua da dugc thao luan tren ca sd so sanh dp day
Idp
Fe vdi cac
dp dai dac trung cho hieu irng bl mat va dp day dac trung cho
sir
hinh thanh vach
ddmen.
Sir
md ta va md
hinh
ly thuyet ly giai cu
thi
da dugc trinh bay trong 01
Khoa luan tdt nghiep
ciia
sinh vien Nguyin Thanh Trung (2003) [15] va trong 03
bai bao da dugc cong bd tren cac tap
chi
Khoa hpc, trong dd, 01 bai bao dang tren
tap chl Qudc te vl Tir hpc va Vat lieu tir (J. Magn. Magn. Mater., North-Holland,
2003) va 01 bai bao dang tren tap
chi
Vat ly Qudc te (PhysicaB, 2003) (xem phu luc
kem theo).
MoH
(T)
^loH
(T)
^oH
(T)

Hinh
3.
Dudng
cong
tir
tri
do theo phuang song song (II)
va
vuong goc
(1)
ciia
cac
mdng ba lap
FelTerfecohanlFe
sau khi
ii
d
nhiet
do
T^
=
450
TT
2.2.C,
Mdng da
lap
TerfecoHonlY^Fcj.^
vd
TerfecoHanlYJFeCo)^,^
Cac mang da

Idp {Terfecohan/Y^Fei.Jn
va
{TerfecoHan/Y,(FeCo),.J^
vdi cac
ndng dd
ciia
Y khac nhau x = 0; 0,1; 0,15 va 0,2 da dugc che tao va nghien
ciiu
thanh cong. Cac ket qua nghien
ciiu
ve cdu triic vi md tren cac he mdu nay da chi ra
rang vdi cac mang sau khi che tao,
Idp
tir giao Terfecohan cd cdu triic vd dinh hinh
trong khi cau triic
ciia Idp
tir
mIm
Y^(FeCo),.^
phu thupc manh vao ndng dp
ciia
Y:
20
la tinh
th^
vdi
Fe(Co),
nand tinh
thi
vdi

Yo,,(FeCo)n,9 (hinh
4b) va vd dinh hinh vdi
Y().2(FeCo)(,
R
(hinh 4a).
K^t
qua nay md ra kha nang che tao cac
Idp
nand tinh the
YFeCo trong mang da
Idp
{a-Terfecohan/n-YFeCo) bang
each
dilu chinh ndng dp
Y dl thu dugc cac
tinh
chdt tir
mIm
va tir giao tdt.
(a) (b)
Hinh
4,
Gidn
do nhiiu
xg tia Xciia cdc mang
TerfecohanlYJ^e,,^
ngay sau
khi che tao (a) va
dnh
chup hien

vi
dien tu truyen qua dp phdn gidi
cao
ciia mdng TerfecohanlYo jFCf^g
(b)
Viec che' tao cac mang mdng da
Idp
{Terfecohan/(Y(Fe,Co)} cd cdu triic kieu
spring - exchange da tao ra cac vat lieu tir giao to hgp cd
tinh
chdt tir va tir giao sieu
mIm.
Cac nghien
ciiu
vl
tinh
chat tir va tir giao tren cac mang nay cho thdy qua
trinh pha tap Y vao vdi ndng dp tdi ban khdng lam giam gia tri tir giao bao hoa ma
tral lai
cdn lam cho dp cam tir giao tang manh dac biet la trong viing tir trudng thdp:
Dp cam
tir
giao
dal cue
dai
X\n=
30x10'^
T'
va^>,//=
15,3x10^

T' thu dugc tren cac
mang
{Terfecohan/Yo
iFeogj^
va
{TerfecoHan/Yo,(FeCo)o9)n
tuang
ling
(hinh 5)
Gia tri dd cam tir giao thu dugc tren cac mang nay
Idn
ban mot bac do
Idn
so vdi gia
tri dp cam tir giao tren mang dan
Idp
TerfecoHan da cong bd.
Cac nghien
ciiu
vl
linh
chdt tir - dien trd cung da dugc
ti^n
hanh tren bai he
mdu nay. Ket qua nghien
ciai
cho thdy he sd tir dien trd GMR cd gia tri nhd MR =
0,25%
va cd qui
luat

phu thupc theo tir trudng gidng nhu tir giao (hinh 6). Dilu dd
hoan toanphu hgp vdi cac ly giai vl
tinh
chdt
tix
tren cac he mang td hgp nay.
21
800
XDCWX^-0O-O(
^
600
400
200
0
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30
20
C
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?l
-10
-20
-30
.
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1
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r—
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a
I
ONJK
§
'
-
(b)
_
1.1.
-40
-20 0 20
u
H (mT)
40 60
-60
-40
-20
0 20
u
H (mT)
40 60
Hinh
5.
Dudng cong tit gido tong cong
(a)
vd

do
cam
tit gido
song song
(b) cua cdc
mdng
da
lap TerfecohanlYfj iFe^g
sau khi
it
d
nhiet
do
T^
=
350
"C
Cac ket qua
va
cac
ly
giai
chi tie't
da
dugc xudt ban trong
05 cong trinh khoa hpc tren cac
tap
chl
khoa
hpc va cac hdi

nghi khoa hpc trong
dd
01
bai
bao dang tren
tap
chi
Qudc
td
vl
Tir hpc va Vat
lieu
tir (J.
Magn. Magn. Mater., North-
Holland, 2003)
va 01 bao cao
tai Hdi nghi Qudc te'
vl Vat ly
va Ky thuat (CHLB
Diic,
2003)
(xem phu luc kem theo).
0.00
-0.05
-0.10
^
-0.15
-0.20
-0.25
CDD

O
I
O
1(3)1
O O
o
oooo
8i
9
o<xxDcx:ixDcaxa>
-0.30
-0.6
91
8
o ODaaDaoooD-o
J
I I L.
-0.4 0.4
-0.2
0.0 0.2
K^
(T)
Hinh
6.
Dudng cong tir -
dien trd
ciia mdng
da Idp
TerfecohanlYo2(FeCo)fj ^
0.6

!
2.2.d.
Nghien
citu
itng dung
vat lieu
tir
giao dang mang mdng TerfecoHan
da
dugc nghien
cihi
ling dung
trong viec che tao sensa do
tir
trudng dua tren hieu
ling
tu
giao
- ap
dien. Sir dung
vat lieu ap dien dang tdm APC
-
855 (American Piezoceramics Inc., PA, USA cung
cdp),
sensa boat ddng nhd
sir kdt
hgp giua hieu
ling
tir giao xudt hien dudi tac dung
cua

tir
trudng ngoai
ciia
vat
lieu
tir
giao
va
hieu
ling
ap
dien thuan,
tiic
la su
xudt
hien the ap dien
Idi
ra
tren
bl
mat cua tinh
thi
ap dien khi tinh the ap dien
bi
bien
dang. Phep
do
dien
the
Idi

ra
tren
hai
cue
cua tdm
vat
lieu
ap
dien dugc thuc hien
22
nhd mdt mach khuyech dai cdng cu tu che' tao vdi he sd khuyech dai bang 1,5.
Kdt
qua nghien
cihi
cho thdy sensa cho dp nhay kha tdt vdi cac mang tir giao cd dd day
2-5
|im.
Ddi vdi cac mang mdng tir giao chua u nhiet cd dp day 5
|.im
va dien tich
5x20
mm^
sensa dat he sd dien - tir dU/dH
-
8 V/T trong vung
tii'
trudng
//// ~
0.1
T

(hinh 7). Dp nhay cua sensa hoan toan cd
thi
dugc tang len bang each tang he sd
khuye'ch dai ciia mach
khuye'eh
dai va sir dung cac mang tir giao cd
tinh
tii
mIm
tdt
(cac mang da
Idp
cd cdu
true kilu
spring - magnets nghien
ciiu).
Cac
kdt
qua nghien
cd'u da dugc trinh bay trong bao cao tai Hdi nghj Vat ly Chdt
rdn
toan qudc
Idn
thir
IV tai Thai Nguyen
(11/2003)
(xem phu luc kem theo). Cdu tao dan gian, gpn nhe
va vdi dd nhay kha cao trong
viing
tir trudng thdp (cd vai

mili Tesla)
cho phep sensa
cd kha nang sir dung lam thiet bi dd va phat hien tir trudng rat
hiJu
hieu.
Kdt
qua nay
r^t
kha quan ddi vdi viec trien khai
ling
dung trong thuc
tiln.
^
1.5 -
7
i:
5
4
T3
0.0
•
r
'•
—1
'
1
'
1
•
1

•
c^
oo ccP/X
- /
o^o
?'
\
-/
\
D°
O,
OOOo
0
\
C-oO
'''-oo,^
-
~o„
o
1
.
1
.
1
.
1
.
1
.
0.0 0.1 0.2 0.3 0.4 0.5

K^
(T)
0.6
Hinh
7.
Dudng cong suthay
doi
ciia the
dp
dien Idi
ra (a) vd he sd dien - tir(b)
theo
tit
trudng ngodi ciia
sensa
3.
KfiT
LUAN
1.
Da che' tao thanh cdng cac mang mdng tir dua tren hgp chdt TerfercoHan:
cac mang dan Idp TerfecoHan, da
Idp
TerfecoHan/YFe, TerfecoHan/YFeCo
va ba
Idp
Fe/TerfecoHan/Fe tren thiet bi
phiin
xa catdt tai Trung tam Khoa
hpc Vat lieu, Khoa Vat ly, Dai hpc Khoa hpc Tu nhien, Dai hpc Qudc gia
Ha

Ndi.
23
2.
Cac mang mdng TerfecoHan dan
Idp
cd di hudng tir vuong gdc. Qua trinh tir
hoa trong cac mang mdng nay la qua trinh quay momen tir tir phuang vuong
gdc vdi mat phang mang sang phuang mat phang mang. Tir giao khdng
Id
dat dugc vao cd
10^
nhung bao hoa d tir trudng cao
(|ioH
> 0,6 T).
3.
Trong cac mang mdng ba
Idp
(sandwich) Fe/TerfecoHan/Fe vdi chilu day
Idp
Fe
(tpe)
tir 5 nm de'n 20 nm, momen tir cua cac
Idp
Fe ndm trong mat
phang mang nhung
mdmen
tir cua cac
Idp
TerfecoHan lech ra khoi mat
phang mang. Ca'u triic tir nhu

vay
cho phep gia thiet su tdn tai cua mdt cdu
triic ddmen dang
90*^
d cac interfaces. Dd ciing la nguyen nhan lam giam tir
trudng bao boa va
thiic
d^y
qua trinh quay xay ra tai tir trudng thdp ban va
tir giao phat
triln
nhanh d tir trudng thdp. Cac mdu ba
Idp
khi
ii
d nhiet dp
TA
< 250
°C
(de khir
ling
sudt) cho dp cam tir giao
Xx//
-
2,5xlO^T*.
Gia tri
nay
Idn
ban gia tri thu dugc tren cac mang mdng dan
Idp.

4.
Khi ii d nhiet dp
T^
>
250
°C,
di hudng tir vuong gdc lai phat triln manh
tren cac mang mdng ba
Idp.
Ngoai ra luc khang tir vuong gdc cdn dat dugc
tdi gia tri
(|ioHc
-^
500 mT). Cac thdng sd nay thoa man dilu kien
ii'ng
dung
cho ghi tii vuong gdc. Ve mat vat ly, ca che'
lire
khang tir vuong gdc cao nay
da dugc giai thich bang
sir
hinh thanh cdu triic nand trong
Idp
Fe d tren bl
mat. Ket qua nay da dugc khang dinh bang cac nghien
ciiu
anh hien vi dien
tir truyin qua.
5.
Cac dac trung

iu
- dien trd tren cac mang da
Idp
TerfecoHan/YFe va
TerfecoHan/YFeCo da dugc khao sat. Dudng cong tir
tri
R(H) cd dang
gidng nhu dudng cong tir giao
X(H),
tuy nhien, he sd tir - dien trd
chi
dat cue
dai MR = 0,2%. Ket qua nay cho phep nhan xet
rdng,
cdu
hinh
tir dp vuong
gdc trong cac mang mdng da
Idp
cd the dugc xem xet nhu la cau hinh
ciia
dien trd
Idn.
Dudi tac dung cua tir trudng ngoai, cdu triic tir ddi thanh song
song vdi dien trd be. Do la kha nang
tilm dn
cua
mgt
cdu hinh tir - dien trd
mdi.

Tuy nhien, trong cac vat lieu dang xet, do cac dien tir 4f cd dp linh
ddng thdp, nen he sd tir - dien trd quan sat dugc cd gia tri be. Cac nghien
24