Preparation and physical properties of quaternary Mn2FeSi0.5Al0.5 alloy powders with heusler and β-Mn structures

Abstract

Manganese-based alloys with the composition Mn2FeZ (Z = Si, Al) have been extensively investigated in recent years due to their potential applications in spintronics. The Mn2FeSi alloy, prepared in the form of ingots, powders, or ribbons, exhibits either a cubic full-Heusler (L21) structure, an inverse-Heusler (XA) structure, or a combination of both. In contrast, the Mn2FeAl alloy has so far been synthesized only in the form of ingots, featuring a primitive cubic (beta-Mn type) structure. This study focuses on the new quaternary Mn2FeSi0.5Al0.5 alloy synthesized from pure Mn, Fe, Si, and Al powders via mechanical alloying. The elemental powders were ball-milled for 168 h with a ball-to-powder ratio of 10:1, followed by annealing at 550 degrees C, 700 degrees C, and 950 degrees C for 8 h in an argon protective atmosphere. The results demonstrate that annealing at lower temperatures (550 degrees C) led to the formation of a Heusler structure with a lattice constant of 0.5739 nm. Annealing at 700 degrees C resulted in the coexistence of several phases, including the Heusler phase and a newly developed primitive cubic beta-Mn structure. Further increasing the annealing temperature to 950 degrees C completely suppressed the Heusler phase, with the beta-Mn structure, having a lattice constant of 0.6281 nm, becoming the dominant phase. These findings confirm the possibility of tuning the structure of Mn2FeSi0.5Al0.5 alloy powder-and thereby its physical properties-by varying the annealing temperature. The sensitivity of magnetic properties to structural changes is demonstrated through magnetization curves and zero-field-cooled/field-cooled curves in the temperature range of 5 K to 300 K.