Correlation of phase transformations and magnetic properties in annealed epitaxial Fe–Pd magnetic shape memory alloy films

Abstract

Single-crystal-like films are promising candidates for magnetic shape memory (MSM) applications on the microscale. For defect reduction and stress relaxation, we apply a heat treatment to pulsed laser deposited, partial epitaxial Fe–Pd films with different compositions. By recrystallization starting from the epitaxial interface, single-crystal-like films are obtained. Deformation twins being present in the as-deposited state are completely eliminated. The epitaxial (100) orientation allows clear monitoring of the transformation from face centered cubic (fcc) austenite to face centered tetragonal (fct) martensite by x-ray diffraction experiments. Transformation from fcc austenite to fct martensite is hindered by constraints from the substrate. At temperatures down to 125 K residual fcc austenite is present. Magnetic measurements performed down to 50 K indicate that during further cooling the phase transformation to body centered tetragonal martensite occurs. The results show that annealing of laser deposited films is a promising route to obtain epitaxial Fe–Pd MSM films that are suitable for applications.