Unconventional critical behaviour in weak ferromagnets Fe2-xMnxCrAl (0<x<1)

TL;DR

This study investigates the unconventional critical behavior in Fe2-xMnxCrAl alloys, revealing inhomogeneous phases influence critical exponents and suggesting a new class of magnetic critical phenomena.

Contribution

It provides detailed analysis of how cluster glass and Griffiths phase affect critical exponents, indicating a distinct universality class for these alloys.

Findings

Critical exponents vary with Mn concentration.

Deviations from known universality classes observed.

Inhomogeneous phases influence magnetic critical behavior.

Abstract

Recent studies on weak ferromagnets Fe2-xMnxCrAl (0<x<1) reveal the presence of cluster glass (CG) and Griffiths phase (GP) below and above the ferromagnetic transition temperature (TC) [(2019) Sci. Rep. 9 15888]. In this work, the influence of these inhomogeneous phases on the critical behaviour (around TC) of the above-mentioned series of alloys has been investigated in detail. For the parent alloy Fe2CrAl, {\gamma} is estimated as ~ 1.34, which lies near to ordered 3D Heisenberg model, whereas obtained value of {\beta} ~ 0.273 does not belong to any universality class. With increment in Mn concentration, both exponents {\gamma} and \b{eta} increases, where {\gamma} and {\beta} approaches disordered 3D Heisenberg model and ordered 3D Heisenberg model, respectively. The observed deviation in {\gamma} and unconventional value of {\delta} can be ascribed to the increment in GP with Mn-concentration. The trend noted for {\beta} can be attributed to the increment in CG regime with an increase in Mn-content. The self-consistency and reliability of the estimated exponents are verified by the Widom scaling relation and scaling equations of state. Our studies indicate that the critical phenomenon of Fe2-xMnxCrAl (0<x<1) alloys possibly belong to a separate class and is not described within the framework of any existing universal model.