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Volt 54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)

Measurement of magnetic and magneto- transport properties of nanomagnets. Measurement data.

Abstract:

High- precision, high- reproducibility, high- repeatability measurement of magnetic and magneto- transport properties of ferromagnetic nanomagnets using the Hall effect

High-precision measurement of effect of spin-orbit torque (SOT effect): Dependence of magnetic and magneto- transport properties on electrical current

High-precision measurement of effect of voltage-controlled magnetic anisotropy (VCMA effect): Dependence of magnetic and magneto- transport properties on a gate voltage




Measurements

(measurement 1) Measurement of Hall angle vs external perpendicular magnetic field

Nanowire with two Hall probes

Measured hysteresis loop (See below) for gap regions indicates that the etching was stopped in middle of FeB layer

click on image to enlarge it

(1.1) Measurements of Hall angle, Anomalous Hall effect (AHE), Inverse Spin Hall effect (Sample dependence)

(1.2) Spin-orbit torque: Measurement of dependence of Hall angle, Anomalous Hall effect (AHE), Inverse Spin Hall effect on current magnitude and polarity.

(1.3) VCMA: Measurement of dependence of Hall angle, Anomalous Hall effect (AHE), Inverse Spin Hall effect on gate voltage

(measurement 2) Measurement of anisotropy field vs external perpendicular magnetic field

(2.1) Measurement of PMA & Anisotropy field

(2.2) Spin-orbit torque: ""Field- like torque" ""Damp- like torque". Measurement of dependence of PMA on the electrical current .

(2.3) VCMA: ""Field- like torque" ""Damp- like torque". Measurement of dependence of PMA on gate voltage.

(measurement 3) Measurement of magnetization switching under external perpendicular magnetic field

Coercive field is about 40 Oe and retention time is about a few minutes. The retention time is too short for a precise measurement.


 

Details of Measurement Methods are here

 


Volt54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)

 

Hysteresis loop

sample: ud66 (one nanomagnet)

sample: free28 (two nanomagnet)

Sample Volt54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)

click on image to enlarge it

fabrication: EB only,

MgO 220C/360C

Raw data Vol54B.zip (.dat files and origin 9 files)

(7zip (free) download is here)

Conductivity: 0.037-0.06 S/m2

Anisotropy field Hanis =2 kGauss

Coercive field = 5 Oe-50 Oe;

Hall angle measured=350-400 mdeg

Intrinsic Hall angle of FeB= 1145 - 1309 mdeg;

Gap region etched: FeB is partially etched, stopped in middle of FeB

 

Since the nanowire is double- layer, which consists of Ta and FeB layer, the Hall angle αHall, FeB in FeB can be calculated from measured Hall angle αHall, measured (See here) as

where

tFeB, tTa, σFeB,σTa are thicknesses and conductivities of FeB and Ta metals.

 

Kerr Rotation angle MOKE

data of a plain film before nanofabrication

(note) Coercive field and shape of coercive loop is very different for a nanomagnet and film, from which it was fabricated, because of different magnetization switching mechanisms (See here)
click on image to enlarge it

kdouble=3.2727

 

 

 

 

 

sizes (nm):
free28 1000
free29 400
ud40 1000 x 500
ud47 400 x 200

 

 

 

 

 

 

 

(measurement 1) Measurement of Hall angle vs external perpendicular magnetic field Hz

 

 

 

 

Hall angle, Anomalous Hall effect (AHE), Inverse Spin Hall effect (Sample dependence)

Hall angle αHall

1st derivation ∂αHall/∂Hz

2nd derivation 2αHall/∂Hz2

αHall and therefore strength of AHE is substantially different for each nanomagnet ∂αHall/∂Hz is different for ~10 % for each sample with correspondent difference of 2αHall/∂Hz2, which means that the strength of ISHE is different for each nanomagnet  

details of this measurement method is here

Sample Volt54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)
click on image to enlarge it

 

Fitting of Hall angle

The Hall angle αHall , its 1st derivation ∂αHall/∂Hz and its 2d derivation 2αHall/∂Hz2 is simultaneously fitted by equation (See here)

where αOHE is Hall angle of Ordinary Hall effect, αAHE is Hall angle of Anomalous Hall effect and where αISHE is Hall angle of Inverse Spin Hall effect

There is an ambiguity for αISHE and αAHE, which depends on unknown spin polarization sp

where sp is the spin polarization of conduction electrons, αAHE,0.5 is αAHE at sp=0.5, αISHE,0.5 is αISHE at sp=0.5

result of fitting:

sample:( free29 gate) αISHE,0.5= 1024 mdeg; αAHE,0.5= 262 mdeg; αOHE=0.2 mdeg/kG; Hp=3.53 kG;

sample:( free28 gate) αISHE,0.5= 551 mdeg; αAHE,0.5= 675 mdeg; αOHE=0.2 mdeg/kG; Hp=3.954 kG;

sample:( free28 gap) αISHE,0.5= 853 mdeg; αAHE,0.5= 313 mdeg; αOHE=0.2 mdeg/kG; Hp=9.65 kG;

sample:( ud40 gate) αISHE,0.5= 161 mdeg; αAHE,0.5= 318 mdeg; αOHE=0.2 mdeg/kG; Hp=3.17 kG;

 


 

AHE & ISHE vs current & current polarity. SOT effect

Measurement 1. Dependence of Anomalous Hall effect (AHE) & Inverse Spin Hall effect (ISHE) on current and current polarity. Effect of Spin-Orbit Torque (SOT)

 

Spin-orbit torque. Hall angle, Anomalous Hall effect (AHE), Inverse Spin Hall effect vs current

fig.4a. Current- dependence of AHE (Hall angle αHall)

fig.4b. Current- dependence of ISHE (∂αHall/∂Hz i)

   

fig.4c. Dependence of AHE on polarity of current j

fig.4d. Dependence of ISHE on polarity of current j

ΔAHE= (αHall(j)-αHall(-j))/2 ΔISHE= (ISHE(j)-ISHE(-j))/2

fig.4e. Hall angle αHall at different current j

fig.4f.∂αHall/∂Hz at different different current j

sample: free28 gate. Dependence of AHE (αHall) is substantial and obvious sample free28 gate. Dependence of ISHE is weak.

details of this measurement method is here

Sample Volt54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)
click on image to enlarge it

Features

(temperature)

dependence on current magnitude

(AHE vs I2 ): strong 5% (sample ud34: 12%) decrease at current of 50 mA/ μm2; (fig.4a)

(ISHE vs I2 ):moderate, 0.4 mdeg/kG decrease at 50 mA/ μm2 (fig.4b)

(Spin- orbit torque)

dependence on current polarity

(AHE(I)-AHE(-I)):strong 0.6-1.2 %; slope: negative (except two gap measurements) ; saturation: at 25 mA/ μm2; (fig.4c)

(ISHE(I)-ISHE(-I)): small (~0.2 mdeg/kG) (fig.4d)

 


AHE & ISHE vs gate voltage. VCMA effect

Measurement 1. Dependence of Anomalous Hall effect (AHE) & Inverse Spin Hall effect (ISHE) on gate voltage. Effect of Voltage-Controlled Magnetic Anisotropy (VCMA)

 

VCMA. Hall angle, Anomalous Hall effect (AHE), Inverse Spin Hall effect vs gate voltage

fig.5a. dependence of AHE (Hall angle αHall) on gate voltage

fig.5b. dependence of ISHE (∂αHall/∂Hz) on gate voltage

normalized change of AHE vs gate voltage. normalized AHE=(AHE(V)-AHE(V=1))/AHE(V).  

fig.5c. Hall angle αHall at different different gate voltages

fig.5d.∂αHall/∂Hz at different different gate voltages

Sample ud40. Dependence on Vgate is weak, but clear Sample ud40. Dependence on Vgate is weak, but clear.

details of this measurement method is here

Sample Volt54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)
click on image to enlarge it

Features

 

dependence on gate voltage

(AHE vs Vgate ): moderate 1.5 % ; slope: unclear

(ISHE vs Vgate ): moderate 0.7 mdeg/kG; slope: negative; saturation: = Vgate=+1 V

 

 

 

 

 


(measurement 2) Measurement of anisotropy field vs external perpendicular magnetic field Hz

details about measurement method is here and here

 

Measurement of PMA. Anisotropy field

Anisotropy field Hanis

Offset magnetic field Hoff . Scan is along wire.

Offset magnetic field Hoff . Scan is perpendicularly to wire.

Anisotropy field Hanis vs external perpendicular magnetic field Hz. Hanis is about 5 kG and variation from sample to sample is about 0.5 kG. Up to =2.5 kG, there is a peak and diversion from a strait line. There is a weak difference between positive and negative scans of Hz. Offset magnetic field Hoff measured when in-plane magnetic field is scanned along metallic wire. There is a substantial difference between samples and a substantial difference between positive and negative scans of Hz. At Hz =7 kG, Hoff = between 50-100 G for different samples. The dependence is linear with some periodical modulation. Offset magnetic field Hoff measured when in-plane magnetic field is scanned perpendicularly to metallic wire. There is a substantial difference between samples and a substantial difference between positive and negative scans of Hz. At Hz =7 kG, Hoff = between -10-40G for different samples. The dependence is slightly linear (nearly a constant) with a substantial periodical modulation.

details of this measurement method is here

Sample VolB54: Ta(3 nm)/ FeB(1.1 nm)/ MgO(7 nm)/ W(1 nm) /Ru(5 nm)
click on image to enlarge it

 

Spin-orbit torque vs PMA

Spin-orbit torque. Measurement of dependence of PMA on the electrical current j.

"Field- like torque". Current- dependence of offset field ∂Hoff/∂j. Scan is along wire.

"Damp- like torque". Current- dependence of offset field ∂Hoff/∂j. Scan is perpendicularly to wire.

∂Hoff/∂j~ 0.1 Gauss/(mA/ μm2).E.g. at j=100 mA/ μm2, change of offset field ΔHoff=10 Gauss. There are clear oscillations. There is a substantial difference between positive and negative scans of Hz. ∂Hoff/∂j~ 0.18 Gauss/(mA/ μm2).E.g. at j=100 mA/ μm2, change of offset field ΔHoff=18 Gauss. There are clear oscillations. There is a substantial difference between positive and negative scans of Hz.

Current- dependence of anisotropy field∂Hanis/∂j. Scan is along wire.

Current- dependence of anisotropy field∂Hanis/∂j. Scan is perpendicularly to wire.

∂Hanis/∂j~ 0.8 Gauss/(mA/ μm2).E.g. at j=100 mA/ μm2, change of anisotropy field ΔHanis=80 Gauss. There are clear oscillations. Amplitude of oscillations increases at a larger Hz. There is a substantial difference between positive and negative scans of Hz. ∂Hanis/∂j~ 0.8 Gauss/(mA/ μm2).E.g. at j=100 mA/ μm2, change of anisotropy field ΔHanis=80 Gauss. There are clear oscillations. Amplitude of oscillations increases at a larger Hz. There is a substantial difference between positive and negative scans of Hz.

details of this measurement method is here

Sample Volt54B Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)
click on image to enlarge it

 

Spin-orbit torque. Measurement of dependence of anisotropy field Hanis and offset magnetic field Hoff on the electrical current j.

"Field- like torque". Dependence of offset magnetic field Hoff on current j. Scan is along wire.

"Damp- like torque". Dependence of offset magnetic field Hoff on current j. Scan is perpendicularly to wire.

Dependence of anisotropy field Hanis on current j.

Dependence is linear. Slope is positive. Measurement is under perpendicular magnetic field H is + 0.8 kG. Dependence is linear. Slope is positive. Measurement is under perpendicular magnetic field H is + 0.8 kG. Hanis is proportional to j2 due to heating. Also, Hanis is proportional to polarity of current due to SOT effect (dependence is different for +j and -j current). Measurement is under perpendicular magnetic field H is + 0.8 kG.

Dependence of offset magnetic field Hoff on perpendicularly applied magnetic field H. Scan is along wire.

Dependence of offset magnetic field Hoff on perpendicularly applied magnetic field H. .Scan is perpendicularly to wire.

Dependence of anisotropy field Hanis on perpendicularly applied magnetic field H

. .  

Data of Sample free 28 gate

details of this measurement method is here
click on image to enlarge it

 

 


 

VCMA vs PMA

 

VCMA. Measurement of dependence of PMA on gate voltage

dependence of anisotropy field on gate voltage ∂Hanis/∂V. Scan is along wire.

dependence of anisotropy field on gate voltage ∂Hanis/∂V. Scan is perpendicularly to wire.

   

dependence of offset field on gate voltage ∂Hoff/∂V. Scan is along wire.

dependence of offset field on gate voltage ∂Hoff/∂V. Scan is perpendicularly to wire.

   

details of this measurement method is here

Sample Volt54A Ta(2.5 nm)/ FeB(1.1 nm)/ MgO(6 nm)/ Ta(1 nm)/ Ru(5 nm)
click on image to enlarge it

 

 

 

 


 

 

(measurement 3) Measurement of magnetization switching under external perpendicular magnetic field Hz

 

Coercive field is about 40 Oe and retention time is about a few minutes. The retention time is too short for a precise measurement.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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