Structural and magnetic characterization of the Ni55Fe19Ga26 shape memory alloy thin film

Abstract

The structural evolution of the Pulsed Laser Deposited Ni55Fe19Ga26 ferromagnetic Heusler alloy thin films has been studied as a function of substrate temperature. Room temperature Grazing Incidence X-Ray Diffraction (GIXRD) measurement reveals the polycrystalline nature of the films consisting of cubic austenite and non-cubic martensite phases. The cubic phase consists of the mixture of an ordered (L21) and disordered (γ) phases, the disordered phase gets suppressed with an increase in the substrate temperature while low temperature X-Ray Diffraction study shows structural modification of the samples. Field Emission Scanning Electron Microscopy (FESEM) study shows the droplet-like morphology of the films. Extended X-ray Absorption Fine Structure (EXAFS) study agrees with the X-ray diffraction results about the phase evaluation and further reveals the local structure information of the constituent atoms which leads to the hybridization effect and finally govern the macroscopic properties of the material. In addition, magnetization studies show the ferromagnetic nature of the film with a mixture of anti-ferromagnetic ordering arising due to antisite disorder of the atoms revealed by the EXAFS measurements.