Rare coexistence of disorder-induced Griffiths phase and reentrant spin-glass state in a Heusler alloy Rh2FeAl with high Curie temperature

Abstract

In this work, we report the synthesis of a Heusler alloy Rh2FeAl with valence electron count (VEC) 29 forming in B2-type structural disorder, where Fe atoms are distributed randomly with Al atoms between 4a and 4b Wyckoff positions (space group Fm3¯m, No: 225). Despite the structural disorder among the moment carrying Fe atoms, the compound exhibits ferromagnetic Curie temperature around TC ∼ 497 K. Nevertheless, the observation of Griffiths-phase (GP) like behaviour at TG ∼ 592 K suggests that atomic disorders brought down the bulk TC by about 95 K. The structural disorder also affects the ordered spin arrangements below TC through the development of a reentrant spin glass (RSG) state at low temperature. Both the GP like behaviour as well as RSG states are rarely observed in Heusler alloys while their coexistence is even rarer. The isothermal magnetisation as well as temperature dependence of resistivity behaviour ruled out the possibility of having half-metallic ferromagnetic characteristic in this material.