Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Cr2O3 is an exceptional antiferromagnet with an easy axis of anisotropy that exhibits a magnetoelectric effect at room temperature [1]. Although there are technological challenges to use it for applications because of the relatively low bulk Neel temperature of TN = 308 K, there are demonstrations that TN can be substantially enhanced by strain in thin films. The morphology and growth procedure of such samples allow the appearance of flexomagnetic effects and pinning of domain walls at grain boundaries [2,3].

Here, we propose a material model of granular antiferromagnetic films and apply it to maze-like domain patterns in thin Cr2O3 samples [4]. The domain pattern is obtained by means of the nitrogen vacancy magnetometry and compared with spin-lattice simulations. We analyze the statistics of the size and self-similarity of the domain wall patterns to correlate the experimental measurements with the parameters of the theoretical model and compare the domain wall patterns with predictions made by a machine learning approach. The estimated inter-grain coupling is characterized by a substantial reduction of the effective exchange coupling to about 10% of the bulk value, with a wide standard deviation. Based on the material model, we provide design rules for the granular AFM recording media.