Ultrathin Chromia on a Hexagonally-Ordered d⁰ Ferromagnet: Evidence of Interfacial Exchange Bias at the Cr₂O₃/TiO_2–x Interface

Abstract

Heterostructures consisting of 10 Å thick chromia films and 50 Å thick titania films display significant exchange bias at and above room temperature. Chromia films ∼10 Å thick were deposited by molecular beam epitaxy (MBE) of Cr at room temperature in ultrahigh vacuum on 50 Å thick TiO2–x (111) films (x < 0.3) also deposited epitaxially by MBE on Al2O3(0001). Cr deposition yields increased Ti­(III) formation in the titania substrate and the formation of a Cr2O3 overlayer, without Cr/Ti interfacial mixing, as determined by in situ photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). In situ low-energy electron diffraction (LEED) and XPS data indicate that the chromia overlayer is hexagonally ordered and ∼10 Å thick. Longitudinal and polar magneto-optic Kerr effect (MOKE) measurements at 285–315 K provide evidence of strong exchange bias between the boundary layer magnetization of chromia and the ferromagnetic substrate. These data demonstrate the robust room-temperature interaction of the boundary layer magnetization of a multiferroic antiferromagnet with a d0 ferromagnetic substrate.

Magnetron Sputtering of Transition Metal Oxynitrides and Their Characterization with Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy

“…Two different forms of PVD include molecular beam epitaxy (MBE) [2] and magnetron sputter deposition-discussed here. MBE is often used for the formation of highly ordered films of rigorously controlled stoichiometry [3]. Magnetron sputtering, however, typically exhibits higher film deposition rates, and good repeatability, albeit with often the formation of polycrystalline films [1] 1…”