Abstract
The present work reports on the new soft ferromagnetic Heusler phases FeNiGe, FeCuGa, and FeCuAl, which in previous theoretical studies have been predicted to exist in a tetragonal Heusler structure. Together with the known phases FeCoGe and FeNiGa these materials have been synthesized and characterized by powder x-ray diffraction, Fe Mössbauer spectroscopy, superconducting quantum interference device, and energy-dispersive x-ray measurements. In particular Mössbauer spectroscopy was used to monitor the degree of local atomic order/disorder and to estimate magnetic moments at the Fe sites from the hyperfine fields. It is shown that in contrast to the previous predictions all the materials except FeNiGa basically adopt the inverse cubic Heusler () structure with differing degrees of disorder. The experimental data are compared with results from ab initio electronic structure calculations on local-density approximation level incorporating the effects of atomic disorder by using the coherent potential approximation. A good agreement between calculated and experimental magnetic moments is found for the cubic inverse Heusler phases. Model calculations on various atomic configurations demonstrate that antisite disorder tends to enhance the stability of the structure.
5 More- Received 5 December 2012
DOI:https://doi.org/10.1103/PhysRevB.87.064411
©2013 American Physical Society