Authors: Dr. James Michels, Dr. Sunil Labroo Department of Physics & Astronomy - SUNY Oneonta

Magnetic Thin Film Analyses using an Optical Modulation System

Objective • Assess Magnetic Thin Film Alloy Physical Properties

• Provide Educational Research Project (Solid State Physics)

Approach • Investigate Magnetic Hysteresis Effects

• Two Experimental Methodologies:

(1) Extraordinary Hall Effect Resistance Measurements

(2) Magneto-Optic Kerr Effect (MOKE) Data

Prior Extraordinary Hall Effect Data and Observations

Prior Magneto – Optical Analyses

0.83 mT

2.0 mT

5.0 mT

8.1 mT

12.0 mT

0.00

0.50

1.00

1.50

2.00

-25 -20 -15 -10 -5 0 5 10 15 20 25

Hall R

esis

tan

ce

(m

Ω)

B (mT)

Hall Resistance vs B-Field 20% Cu in Ni

Increasing B-field

Decreasing B-field

Increasing B-field

Ordinary Hall Effect

(metals and semi-conductors)

x( )L d

q E v BF

Extraordinary Hall Effect

(concentrations of magnetic materials)

0 0e

EH

R B R MR

t

0H

H

R BVR

I t

0

Current

Ordinary Hall Coefficient

I

R

0

Extraordinary Hall Resistance

Extraordinary Hall Coefficient

Permeability of free space

Magnetization

EH

e

R

R

M

Extraordinary Hall Effect Experimental Setup

Sample Specifications

• Film thicknesses of 2300-2500 Å

• Current results for the 20% Ni in Cu setup • Other sample compositions: 1%, 5%, and 10%, Ni in Cu • Atomic fractions prepared using arc melting / thermal evaporation

drift velocitydv

B

electric field vectorE

HV

Lorentz Force

t

h

I I

B

B

y

x

z

eF

ev

LF

dv

+ + + + + + + + + + + +

- - - - - - - - - - - - -

HV- +

Magnet

Pole

Magnet Pole Magnetic

Field Vector

Hall

Voltage

Hall Resistance

Magneto - Optic Kerr Effect (MOKE) Apparatus

HV

HV

Future Magneto-Optical Analyses

• Kerr Cell Analyses

• Birefringence Analyses

• Structural Analysis – Magnetostriction (stress / strain)

• Optical Communications

• Spectral Analyses

Laser

Polarizer

Polarizer

(Analyzer)

Electomagnet

Poles

Photoelastic

Modulator (PEM)

Light

Detector Thin

Film

Light

Chopper

Lock-in

Amplifier Oscilloscope

Computer

[1] [Tb0.4Fe0.4/Fe0.5Co0.5]3

multilayer film [2] Gd-Co film at several

optical wavelengths

References

[1] Cerne, J., Magneto-Polarimetry Advanced Lab, Univ. Buffalo.

[2] Sata, K., Jap. J. of Applied Physics, Vol. 20, No. 12, Dec. 1981

• CuNi alloy thin films • Concentrations of Ni in Cu (1%, 5%, 10%, 20%, 50%)

Alternative Magneto-Optical Applications