Antiferromagnetism in γ-Phase Mn-Ir Alloys

概要

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Crystallographic and magnetic properties were studied in the disordered γ-phase Mn_<1-x>Ir_x(0.05<x<0.35) alloys. In Mn rich alloys, tetragonal distortion with axial ratio c/a>1 occurs at a temperature below their Neel temperature, T_N. The tetragonal distortion temperature, T_d in the antiferromagnetic ordered state decreases rapidly with increasing Ir and the alloys with x>0.15 remain cubic down to low temperatures. On the other hand, T_N Increases with alloying Ir at a rate of about 9K/at%Ir up to 730K at x=0.25 and it is extrapolated to 500±20K for fcc Mn. It was concluded that the anomalous rise of T_N is not mainly attributed to atomic order nor to the enhancement of exchange interaction due to lattice expansion, but that the perturbation of band structure due to alloying leads to stronger magnetic interaction. A Cu_3Au type atomic ordering in the vicinity of x=0.25 was found to raise the T_N by about 200K. The origin of tetragonal distortion is discussed.
社団法人日本物理学会の論文
1974-02-15