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Electric field manipulation of magnetization at room temperature in
multiferroic CoFe2O4/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 heterostructures
J. J.
1
Yang,
Y. G.
1,a)
Zhao,
H. F.
1
Tian,
1
Luo,
L. B.
H. Y.
1
Zhang,
Y. J.
1
He,
and H. S.
2
Luo
1Department
of Physics and State Key Laboratory of New Ceramics and Fine Processing,
Tsinghua University, Beijing 100084, People’s Republic of China
2State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute
of Ceramics, Chinese Academy of Sciences, Shanghai 201800, People’s Republic of China
I. Introduction and objective
IV. Electric field control of the magnetic anisotropy of
CFO films in CFO/PMN-PT heterostructures
(a)
(b)
100
250
H∥
H∥
3
M ( emu/cm )
200
3
Magnetic field
200
0
0V
400 V
0V
-100
250
(c)
200
150
(d)
3
M ( emu/cm )
-200
H⊥
0
H⊥
-200
-10
-5
0
5
H (kOe)
10
0
6 (e)
5
H (kOe)
100
10
(f)
0
M/M(0) (%)
 Objective
We have fabricated the CFO/PMN-PT heterostructures and studied the
properties of electric field control of magnetization.
150
0V
400 V
0V
-100
Considering the large magnetostriction of CFO and excellent piezoelectric
activity of PMN-PT single crystal, the CFO/PMN-PT heterostructure is a
good candidate for the study of ME coupling effect. However, there have
been no reports on CFO/PMN-PT heterostructure.
M ( emu/cm )
200
3
100
4
2
-2
0
-4
H⊥
H∥
-2
-6
-9 -6 -3 0 3 6
E (kV/cm)
9
-9 -6 -3 0 3
E (kV/cm)
6
9
M/M(0) (%)
Multiferroic materials with magnetoelectric (ME) coupling have attracted
much attention due to their interesting
P
M
properties and potential applications.
+ - + Because single phase multiferroic
+ - + N
S
materials are rare, multiferroic heterostructures provide an alternative way
for exploring ME effect via accurately controlled interface. In these
studies, one of the key issues is the manipulation of magnetism by electric
field and the work on this aspect is still limited.
 CoFe2O4/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (CFO/PMN-PT) heterostructures:
Electric field
M ( emu/cm )
Multiferroic materials and multiferroic heterostructures:
 In-plane (out-of-plane) magnetization of CFO films increases (decreases)
under out-of-plane electric field and
restores to its initial values after
removal of the electric field.
The electric field elongate the outof-plane lattice parameter of PMN-PT
through the converse piezoelectric
effect and thus enhances σ100, resulting
in an increase in Kme. As a result, the
in-plane (out-of-plane) magnetization
increases (decreases) under electric
field.
The in-plane and out-of-plane
ΔM/M(0)−Electric field loops have
butterfly shape, which agree with the
strain-electric field loop of PMN-PT
single crystal. And the derived
maximal ME coupling coefficient
α=μ0dM/dE is 3.2×10−8 s m−1.
II. Methods
10
3
10
(b)
2
-40 -20 0 20 40
0
E (kV/cm)
H∥
H⊥
-100
2 ( )
o
-10
M ( emu/cm )
H∥
M ( emu/cm )
206
166
-5
0
5
V (V)
0
-40
40
(b)
V (V)
3
208
0
164
H⊥
300
600
900
1200
-40
1500
Time (s)
(c)
(d)
c a
b
+ (e)
- - -
- - P
+ + +
After poling
P
+ + +
+50 V -
-
- -
+
+
+
P
-50 V +
The manipulation of magnetization of
CFO films by electric voltages with
different polarities was realized. The
manipulation of magnetization is
reversible
and
the
change
of
magnetization is sharp. These are also
consistent with the in-plane stress
anisotropy energy.
The sharp and reversible ME coupling
coefficient α=μ0dM/dE is 2.5×10−8 s m−1.
These values is comparable to that of
CoFe2O4 nanopillars in a BiFeO3 matrix
(~10−8 s m−1).
-200
-300
20 30 40 50 60 70 80
40
(a)
0
3
100
1
10
210
200
PMN-PT
(003)
10
40
20
0
-20
-40
PMN-PT
(002)
5
300
M ( emu/cm )
7
PMN-PT
(001)
Intensity (cps)
10
(a)
CFO (004)
9
P ( C/cm )
III. XRD and magnetic property of the
multiferroic CFO/PMN-PT heterostructures.
V. Electric field manipulation of magnetization in
CFO/PMN-PT heterostructures
3
CFO films were grown on PMN-PT (001) substrate by PLD. The
thickness of the films is about 200 nm.
The magnetization of the CFO films was measured by a SQUID
(MPMS-XL7). The voltage was applied in situ on the sample by an
electrometer (6517A, Keithley) during the magnetic measurement.
10
H (kOe)
XRD data show that CFO films are single-phase and (004) oriented.
The in-plane and out-of-plane magnetic hysteresis loops of CFO films
show that a small magnetic anisotropy exists with the out-of-plane
direction as the magnetic hard direction. This is consistent with the inplane stress anisotropy energy E=Kmecos2θ, where anisotropy constant
Kme= -3λ100σ100/2 , λ100= -350×10-6 for CFO films and σ100<0 for
compression.
VI. Conclusion
The manipulation of magnetization by electric field at room temperature was
realized. And the results can be understood by the picture of electric field control of
magnetic anisotropy.
A large ME coupling coefficient was observed in the multiferroic CFO/PMN-PT
heterostructures, which is comparable to that of CoFe2O4 nanopillars in a BiFeO3
matrix (~10−8 s m−1).
Publication: Appl. Phys. Lett. 94, 212504 (2009)