Magnetic compensation in Mn4-xCuxN films on SrTiO3(001) with noncollinear magnetic structures

We present that Mn4-xCuxN films grown by molecular beam epitaxy on SrTiO3(001) have a magnetic compensation (MC) composition with noncollinear magnetic components at room temperature. Due to the high crystalline quality and perpendicular magnetic anisotropy, the remanent magnetization ratio was almost 100% for x <= 0.6. At 0.10 <= x <= 0.15, the saturation magnetization was the smallest, while the coercivity was the largest. The hysteresis curves obtained by both the magneto-optical Kerr effect and the anomalous Hall effect showed sign reversal between x = 0.1 and 0.15. X-ray magnetic circular dichroism (XMCD) spectra at the Cu L-2,L-3 edges also showed sign reversal over the entire energy range. These results provide evidence that the MC composition is in the vicinity of x similar to 0.1. However, the XMCD spectra at the Mn L-2,L-3 edges showed a different magnetic structure change from that of Ni-doped Mn4N, which also exhibits MC. A magnetic structure model for Mn4-xCuxN is discussed in comparison with the experimental results.