Revealing the Magnetic Structure and Properties of Mn(Co,Ge) 2 .

The atomic and magnetic structures of Mn(Co,Ge) 2 are reported herein. The system crystallizes in the space group P 6 3 / mmc as a superstructure of the MgZn 2 -type structure. The system exhibits two magnetic transitions with associated magnetic structures, a ferromagnetic (FM) structure around room temperature, and an incommensurate structure at lower temperatures. The FM structure, occurring between 193 and 329 K, is found to be a member of the magnetic space group P 6 3 / mm ' c '. The incommensurate structure found below 193 K is helical with propagation vector k = (0 0 0.0483). Crystallographic results are corroborated by magnetic measurements and ab initio calculations.