Evolution of ferromagneticlike order inFe2V1−xCrxAlHeusler alloys

Abstract

Structural, magnetic, and magnetotransport behaviors of ${\text{Fe}}_{2}{\text{V}}_{1\ensuremath{-}x}{\text{Cr}}_{x}\text{Al}$ Heusler-type alloys have been investigated in the present work. From the detailed analysis of data it is observed that increasing Cr content promotes site disorder of Fe and Al, which in turn leads to destabilization of $L{2}_{1}$ superstructure of ${\text{Fe}}_{2}\text{VAl}$. This site disorder seems to enhance the magnetic moment through spatially confined magnetic entities and intercluster interactions, transforming the alloy system into a magnetically ordered state in the limit $x\ensuremath{\rightarrow}1$. Low-temperature magnetoresistance (MR) values drop quite rapidly from $\ensuremath{\sim}10%$ for $x=0$ to 0.4% for $x=0.8$, suggesting that magnetic interactions have a role in MR deterioration. Further the MR exhibits a maximum at a particular temperature in the vicinity of magnetic transition temperature, where interaction effects weaken. Our magnetization data support MR results and suggest that undoped ${\text{Fe}}_{2}\text{VAl}$ exhibits cluster-glass behavior with optimum superparamagnetic (SPM) contribution, developed possibly due to the random anisotropy with the presence of V. However, in Cr-substituted alloys anisotropy reduces due to coupling between the clusters, which, in turn, results in reduced SPM contribution and low MR values.