Ferrimagnetism in sputtered MnxCoGe thin films

Investigations into the magnetic properties of sputtered MnxCoGe films in the range 0.8 <= x <= 2.5 uncovered ferrimagnetic order, unlike the ferromagnetic order reported in bulk samples. These films formed hexagonal Ni2In-type structures in all measured compositions. While the Curie temperatures of the films are comparable to those of hexagonal bulk MnCoGe, here is a reduction in the magnetization of the MnxCoGe film relative to bulk MnCoGe, and a magnetization compensation point is observed in the x < 1 samples. To understand the behavior, we calculated the magnetic moments of Mn-antisite defects in MnCoGe with density-function theory calculations. Models constructed from the calculation suggest that films become ferrimagnetic due to the presence of Mn on the Co and Ge sites. In the x < 1 samples, these defects arose from the disorder in the films, whereas for x > 1, the excess Mn was driven onto the antisites and produced ferrimagnetic order.Comment: 8 pages, 7 figure