Growth-associated emergence of spontaneous magnetization in Al-doped Cr2O3 thin film

Development of antiferromagnetic/ferrimagnetic materials has been an area of active pursuit to advance the antiferromagnetic/ferrimagnetic spintronics. In this paper, we investigated the emergence of the spontaneous magnetization MS in the antiferromagnetic Cr2O3 thin film by the Al substitution. In the case of the (Cr1-xAlx)2O3(0001) thin films, MS increases with increasing Al composition x up to x ∼0.21. The magnitude of MS decreases abruptly for x > 0.22, accompanied with the collapse of the crystal formation. We found that the induction of the spontaneous magnetization was highly associated with the growth process. The magnitude of MS depends on the growth direction of the film: MS at 10 K for x = 0.13±0.01 is 80 kA/m, 30 kA/m and 0 kA/m for (0001), (011¯2) and (112¯0) films, respectively. The difference in MS with the growth direction is relevant to the magnetic sublattice selective substitution of Al during the thin film growth. This specific substitution occurs in the growth plane having the layer-by-layer stacking of the magnetic sublattice, which was verified by the direct observations using the scanning transmission electron microscope.