Disorder and Noncollinear Magnetism in Permanent-Magnet Materials with the \u3ci\u3eThMn\u3c/i\u3e\u3csub\u3e12\u3c/sub\u3e Structure

We report calculations of the noncollinear magnetic structures of YFe12-xMox permanent-magnet materials, using a novel variant of a spin-polarized tight-binding–linear-muffin-tin-orbital technique allowing for local spin-quantization axes on each site and considering spin-orbit coupling. The ternary YFe12-xMox compounds crystallize in the tetragonal ThMn12 structure which can be stabilized only by the partial substitution of Fe by an early transition metal like Mo. We show that the substitutional disorder leads to canted spin structures at low Mo content ( x~1) and to spin-glass-like behavior at higher Mo content (x~3)