Magnetism of α-Cr2O3 epitaxial structures grown on sapphire by the mist-CVD method

Abstract

The magnetic properties of α-Cr₂O₃ structures grown on a sapphire substrate by ultrasonic chemical vapor deposition (mist-CVD epitaxy) have been studied. Three samples have been fabricated. The first of them is very thin and contains only separate small crystallites (islands in the epitaxy plane). The second is a flat layer of submicron thickness, and the third is an analogue of the second layer with randomly attached hexagonal crystallites outside the epitaxial plane. The island structure represents a dilute ferrimagnet. To evaluate the size distribution of crystallites of the island structure, histograms were constructed, which allow assuming a lognormal type of distribution with an average crystallite size of approximately 300 nm. Based on the measured magnetic hysteresis parameters and micromagnetic modeling, estimates for the effective spontaneous magnetizations of the island structure were obtained: for saturation (40–120 kA/m) and saturation remanence (3–8 kA/m). It was shown that the magnetic ordering of the epitaxial layers is close to a weak ferromagnet type, while the island epitaxial structure appears close to a ferrimagnet.