Magnetic Properties and Thermal Expansion of Mn–Sn Alloys

Abstract

The magnetization, linear thermal expansion and hardness of the Mn–Sn alloys furnace-cooled after homogenizing at 1070 K for 10.8 ks have been investigated. The Mn–Sn alloys containing 23.8–24.4% Sn show a stable η-single phase with a hexagonal structure and are antiferromagnetic at room temperature. The alloys containing 24.4%Sn or more show a structure mixed with a ferrimagnetic hexagonal ζ phase. The Mn–Sn alloy with an η-single phase shows a maximum value of magnetization of 0.4×10−6 Wb·m/kg in a wide temperature range below the Néel point. In the mixed phase alloy, the Curie point of ferrimagnetism appears below the antiferromagnetic transition point, and the magnetization increases abruptly with decreasing temperature. The linear thermal expansion of the Mn–Sn alloys with η phase exhibits a relatively low coefficient below the Néel point. A maximum value of spontaneous volume magnetostriction of 0.7×10−2 has been obtained in the Mn-24.4%Sn alloy. This value is about a half of those of the Invar type Mn–Ge alloys. The Mn–Sn alloys show a minimum Vickers hardness of about 300 in the vicinity of the η phase region, and the hardness rapidly increases with decreasing Sn concentration.