title: Coexistence of exchange bias and magnetization pinning in the MnO(x)/GaMnAs system.
abstract: Coexistence of exchange bias (H(E)) and magnetization (M) shift was observed in as-grown and field-annealed MnO(x)/Ga(0.95)Mn(0.05)As bilayers. It was found that H(E) initially decreases with the annealing time t(a) and then increases when t(a) > 30 min, while the M shift remains almost unchanged with t(a). X-ray photoelectron spectroscopy (XPS) analysis reveals that MnO(x) is composed of MnO and Mn(3)O(4), and the volume amount ratio of Mn(3)O(4) to MnO increases with increasing t(a). A simple model based on a uniform MnO-Mn(3)O(4) interface with constant 'pinned' uncompensated interfacial spins is proposed to account for the observed exchange-biased phenomena in the bilayers.
authors.affiliation: Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan.
authors.forename: P W
authors.initials: PW
authors.lastname: Huang
authors.forename: J H
authors.initials: JH
authors.lastname: Huang
authors.forename: C H
authors.initials: CH
authors.lastname: Yen
authors.forename: C Y
authors.initials: CY
authors.lastname: Cheng
authors.forename: F
authors.initials: F
authors.lastname: Xu
authors.forename: H C
authors.initials: HC
authors.lastname: Ku
authors.forename: S F
authors.initials: SF
authors.lastname: Lee