Magnetic Analysis of Polar and Nonpolar Oxide Substrates

The magnetism of different polar and nonpolar cuts of single-crystal oxide substrates has been analysed. In addition to their intrinsic diamagnetism, some crystals exhibit a Curie-law susceptibility, which is associated with 3d impurities at the 1 ppm level, except for MgO where it is ~30 ppm. Others exhibit an anhysteretic ferromagnetic-like signal typical of d⁰ magnetism. The magnitude of the saturation moment depends critically on the type of surface in the case of the perovskite oxide substrates-SrTiO₃, LaAlO₃, and LSAT. The moment on (111) SrTiO₃ reaches a maximum of 80 μB nm^-2 on annealing in vacuum in the region of 650°C but no moment (<;2 μ_B nm^-2) is detectable on (100) SrTiO₃. The moments on the two polar cuts of LaAlO₃ are 40-70 μB nm^-2. No correlation was found between the magnetism and the polar nature of the cut in non-perovskite oxide substrates-MgO, MgAl₂O₄, TiO₂, and Al₂O₃.