Evolution of Spin‐Glass Phase in Antiferromagnetic Mn ₂ FeAl _{1– <i>x</i>} Si _<i>x</i> Heusler Alloys

A thorough investigation of the structural and magnetic properties of Mn 2 FeAl 1– x Si x ( x = 0.4, 0.6, 0.8) Heusler alloys is presented. The alloy with the least Si content crystallizes in a cubic β‐Mn crystal structure ( space group), whereas for higher Si content, the emergence of XA‐type structure ( space group) is observed. The alloy with the highest Si content displays an XA‐type structure with a significant minor phase of cubic β‐Mn. Temperature‐dependent DC magnetization depicts a dominant antiferromagnetic nature (16 K 19.5 K). For x = 0.4, observation of bifurcation in the zero‐field‐cooled and field‐cooled magnetization curves, exponential temperature decay of coercivity and remanence, frequency‐dependent shifting of the peak temperature, and magnetic relaxation and memory effect below the characteristic temperature suggest the presence of low‐temperature spin‐glass (SG) state. However, the samples with higher Si content ( x = 0.6, 0.8) show an unconventional SG behavior, where some SG signatures are evident while others are suppressed, which can be associated to the onset of the XA phase. Interestingly, with increasing Si content, the alloys gradually make a transition from an antiferromagnetic phase with prominent SG features to a purely antiferromagnetic state with weaker SG signatures.