Ultrathin Chromia on a Hexagonally-Ordered d0 Ferromagnet: Evidence of Interfacial Exchange Bias at the Cr2O3/TiO2-x Interface

Heterostructures consisting of 10 A thick chromia films and 50 A thick titania films display significant exchange bias at and above room temperature. Chromia films ~10 A thick were deposited by molecular beam epitaxy (MBE) of Cr at room temperature in ultrahigh vacuum on 50 A 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 A thick. Longitudinal and polar Magneto-optic Kerr Effect (MOKE) measurements at 285 K – 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 intera...