Structural and Hysteretic Properties of Oxidized Epitaxial MgO(100)/57Fe/Cr Films

The structural and hysteresis properties of epitaxial MgO(100)/57Fe(50 nm)/Cr(2 nm) films grown by molecular beam epitaxy (MBE) were investigated. Changes in structural properties during annealing in the temperature range of 200–300°C were studied using X-ray diffraction, Raman spectroscopy, atomic force microscopy and Mössbauer spectroscopy. It was shown that at temperatures above 250°C, oxygen diffusion through the protective Cr layer occurs, leading to the formation of antiferromagnetic α-Fe2O3 oxide. The temperature dependences of hysteresis properties during annealing were determined. At an annealing temperature of 280°C, the coercive force reaches a maximum value of 190 Oe. The absence of exchange bias, evidenced by zero shift in the hysteresis loops, suggests the dominant role of low magnetic anisotropy of α-Fe2O3 and interface disorder in these oxidized heterostructures.