Understanding the effect of foreign atoms occupation on the metamagnetic behaviors in MnCoSi-based alloys: taking Pt-doping as an example.

Present research on TiNiSi-type MnCoSi-based alloys focuses on finding a suitable doping element to effectively reduce the critical magnetic field () required to induce a metamagnetic transition. This paper provides a guide to achieve this goal through an experimental investigation of MnPtCoSi and MnCoPtSi alloys. In MnPtCoSi, asincreases,at room temperature decreases, while in MnCoPtSi, it increases. This phenomenon can be attributed to the fact that larger Pt atoms prefer Co sites over Mn sites, as predicted by our density-functional theory. Consequently, in MnPtCoSi, larger Co atoms are extruded into the Mn atoms chain, increasing the nearest Mn-Mn distance and resulting in a reduced. This finding suggests that transition-metal atoms with more valence electrons preferably occupy the Co site, while those with fewer valence electrons preferably occupy the Mn site. Adhering to this rule, one can easily obtain a lowand large magnetostrain under a low magnetic field by selecting a suitable foreign element and chemical formula, as demonstrated by the MnPtCoSi alloy.