1. Temperature dependence of planar Hall effect of Fe/MgO(001)
Determination of the anisotropy field strength in magnetic films using magneto transport measurement
W. N. Cao, J. Li, Y. Z. Wu
Surface Physics Laboratory (National Key Laboratory), Department of Physics, Fudan University, Shanghai, China
Motivation
The method to determine the magnetic anisotropy of magnetic thin film quantitatively
Hysteresis technique : need to saturate the magnetization
(ROTMOKE)
Anisotropic transport measurement: not necessary to saturate the magnetization
Anisotropic magneto-resistance, Planar Hall effect
External magnetic field<exchange coupling field
No broken exchange coupling
For studying the exchange coupling of magnetic multilayer
Demo the setup of transport measurement(determine the magnetic anisotropy of single-crystal Fe film)
Determine the magnetic anisotropy by ROTMOKE
Sample preparation
Angle dependence of torque curve of Fe/MgO(001)
Sample
Magnet
Laser
Polarizer
Analyzer
Photodiode
MgO(3nm)/ Fe (10nm)/MgO(001)
Grown epitaxially by MBE
Sketch drawing of Hall bar
The Hall bars were along the [100] and [110] direction. The planar Hall effect was measured with a current of 2.5mA along the Hall bar.
fitting curves equation:
l(α)=(1/2)Hk1 sin2θ+(1/4)Hk2 sin4θ
l(α) is the ratio L/VMs(L is a torque, V the volume of the magnetic layer, Ms the saturation magnetization), Hk1 the uniaxial anisotropy,Hk2 the four-fold anisotropy.
Hk1=35±5 Oe; Hk2= 570±9 Oe
Planar Hall Effect (PHE)
Determination of the magnetic anisotropy by PHE θM M I
l(α)=Hsin(α-θ)
black dots and green dots
Vxy
l(α)=(1/2)Hk1 sin2θ+(1/4)Hk2 sin4θ
red fitting curves
Hall bar along [110]， H=1000 Oe
Hall bar along [100]， H=1000 Oe
ρxy=Vxy/I·d= (ρ// − ρ⊥)cos θM sin θM
ρ// and ρ⊥ are resistivities for magnetization vector oriented parallel and perpendicular to the current.
ρ// − ρ⊥
Angle-dependence of Planar Hall effect
Hk1=39±5 Oe, Hk2= 577±9 Oe
Hk1=49±3 Oe, Hk2= 554±6 Oe
Same as results from ROTMOKE except for better signal to noise ratio !
Conclusion
Temperature dependence of planar Hall effect of Fe/MgO(001)
Home-made setup for Planar Hall Effect measurement was finished.
Magnetic anisotropy of Fe/MgO(001) was determined by ROTMOKE and Planar Hall Effect. The results from these two methods are same but better signal to noise ratio can be obtained by Planar Hall Effect.
Linear dependence of Planar Hall Effect on temperature was found from 90K to room temperature.
Planar Hall Effect of Fe/MgO is linearly dependent on temperature .