Transcript 幻灯片 1

Magnetic transport properties
in epitaxial Fe3O4 thin film
Chunrui Hu Yizheng Wu
Surface Physics Laboratory ,Department of Physics, Fudan University
Introduction：
Field dependence of MR% at different temperatures
0
40
Fe3O4(004)
RT Phall effect
300k
300k
5
34
36
0
easy axis [110]
hard axis [100]
-5
2theta
-9
A substantial increase
of the resistivity at the
Verwey transition
occurs at TV ~112 K.
100 150 200 250 300
temp(k)
0
90
180
270
360
angle(degree)
9
field( koe)
No pinnacle is observed
in easy axis; pinnacle in
hard axis may be produced
by Phall effect .
50
0
-50
-100
Phall resistivity：
ρxy=(ρ||-ρ┴)sinθcosθ fit θ，
torque: H*sin(α-θ),
α: H۷I, θ : M۷I.
RT<100>
100
phall(  cm)
current || [110]
current || [100]
0.01
easy axis [110]
hard axis [100]
0
Resistivity as a function of temperature
0.1
6
4
2
0
-2
-4
-6
phall(  cm)
32
60
phall(  cm)
10
7
10
6
10
5
10
4
10
3
10
hall(  cm)
intension
20
RT Hall effect
The 004 reflection from the Fe3O4
film is shown. Laue Oscillations
indicate a very high crystalline
coherence ,which also can be gained
from RHEED pattern.
xx(  cm)
0
Magnetoresistance
reach maximum
round at 110k,
nearly 11%.
field( koe)
8
1E-3
50
-8
-10
9
1
-6
MgO(002)
10
RHEED
-4
-12
-60 -40 -20
Experiment： XRD
10
MBE
10
Fe3O4
MgO(001)
300k
250k
200k
175k
150k
130k
120k
110k
100k
95k
90k
-2
mr( % )
Fe3O4 is one of the important 3d transition-metal oxides, high
Curie temperature (858 K), presence of a metal-insulator
transition MIT at around 120 K (Verwey transition),and spin
polarization rate reaching 100% in theory. Therefore, Fe3O4 is
expected to exhibit suitable properties for its implementation
in spintronic devices.
0
90
180
270
360
angle( degree)
80
60
40
20
0
-20
-40
-60
-80
RT<110>
0 50 100150200250300350400
angle( degree)
Hsin(α- θ) = (1/2)Hk1sin2θ - (1/4)Hk2sin 4θ Fitting:
<100>
Hk1=-11.0319 Oe，Hk2=-286.4634 Oe;
<110>
Hk1=22.1251 Oe, Hk2=-263.5418 Oe.
Hall resistivity as a function of resistivity
Curve fit：
 xy (  cm)
the origin
of this scaling is
an open issue at
present.
-1
σxy~σxx
1.66，
1
conclusion：
0.1
0.01
1E-3
xy42.7nm<110>
xy42.7nm<100>
xy79.2nm<110>
xy24.8nm<110>
1E-4
1E-5
1
10
 (  cm)
xx
-1
100
（1）The epitaxial films of high crystal quality are
gained by Molecular Beam Epitaxy.
（2） Magnetoresistance reach maximum round at 110k.
（3） Pinnacle in hard axis may be produced by Phall effect.