Magnetic structures and their stability inMn3Rhordered and disordered alloys

Abstract

The electronic and magnetic structure of ${\mathrm{Mn}}_{3}\mathrm{Rh},$ including noncollinear structures, in the ordered and disordered states have been investigated by the tight-binding linear-muffin-tin orbital method. A magnetic long-range order of the triangular $(T1)$ structure in the ordered state is reflected in a dip around the Fermi level in the density of states. This characteristic feature can be retained in the multiple-Q spin-density-wave (SDW) structures in the disordered alloy, implying that a stable antiferromagnetic order also remains in the disordered alloy. The most stable structure in the disordered alloy is suggested to be the $3Q\ensuremath{-}\mathrm{SDW}$ structure. From the effective exchange constant, the N\'eel temperature in the disordered alloy is estimated to be about 680 K, close to the experimental value of about 700 K. Compared to the N\'eel temperature of pure \ensuremath{\gamma}-Mn metal, such a high value is pertinent to the change in the electronic structure caused by the addition of Rh.