Exotic magnetic behaviour and evidence of cluster glass and Griffiths like phase in Heusler alloys Fe2-xMnxCrAl (0 ≤ x ≤ 1)

Abstract

We present a detailed study of structural, magnetic and thermodynamic properties of a series of Heusler alloys Fe_2-xMn_xCrAl (x = 0, 0.25, 0.5, 0.75 and 1). Structural investigation of this series is carried out using high resolution synchrotron X-ray diffraction. Results suggest that with increasing Mn concentration, the L2₁ structure of Fe₂CrAl is destabilized. The DC magnetization results show a decrement in paramagnetic (PM) to ferromagnetic (FM) phase transition temperature (T_C) with increasing Mn concentration. From the systematic analysis of magnetic memory effect, heat capacity, time dependent magnetization, and DC field dependent AC susceptibility studies it is observed that, Fe₂CrAl exhibits cluster glass(CG)-like transition approximately at 3.9 K (T_f2). The alloys, Fe_1.75Mn_0.25CrAl and Fe_1.5Mn_0.5CrAl exhibit double CG-like transitions near T_f1 ~ 22 K, T_f2 ~ 4.2 K and T_f1 ~ 30.4 K, T_f2 ~ 9.5 K respectively, however, in Fe_1.25Mn_0.75CrAl, a single CG-like transition is noted at T_f2 ~ 11.5 K below T_C. Interestingly, FeMnCrAl shows the absence of long ranged magnetic ordering and this alloy undergoes three CG-like transitions at ~22 K (T_f^*), 16.6 K (T_f1) and 11 K (T_f2). At high temperatures, a detailed analysis of temperature response of inverse DC susceptibility clearly reveals the observation of Griffiths phase (GP) above 300 K (T*) in Fe₂CrAl and this phase persists with Mn concentration with a decrement in T*.