THE FABRICATION OF HEUSLER ALLOY THIN FILMS FROM MULTIPHASE TARGETS USING PULSED LASER DEPOSITION

Author

Heather M. A. Patton, Southern Illinois University CarbondaleFollow

Date of Award

1-1-2009

Degree Name

Master of Science

Department

Physics

First Advisor

Stadler, Shane

Second Advisor

Aouadi, Samir

Abstract

In this project, we have explored the possibility of growing high quality Heusler alloy thin films from multiphase targets. Bulk targets were found to be partially formed, i.e. not of homogeneous L2₁ structure, through x-ray diffraction measurements. Pulsed laser deposition is a technique that can provide a congruent transfer of material from the target to the substrate, even in some cases where the target is not of a single crystalline phase. It was the objective of this work to determine whether L2₁ structured thin films of Co₂MnAs_xGe_(1-x) could be grown from multiphase targets. Measurements have been carried out to study the magnetic and structural properties of the Heusler alloys Co₂MnAs_xGe_(1-x). The optimization parameters that were investigated were substrate type, growth temperature, laser parameters, film thickness, and other common deposition parameters. Temperature-dependent magneto-optic Kerr effect (MOKE) techniques were used to study the qualitative magnetic properties. Alternating current (AC) susceptibility (using a MOKE technique) measurements were made as a function of temperature to view the second-order transition and obtain the Curie temperatures. Frequency dependent AC susceptibility was measured to determine the frequency dependence of the AC susceptibility for Co₂MnAs_xGe_(1-x).