Revealing the origin of the vertical hysteresis loop shifts in an exchange biased Co/YMnO sub(3) bilayer

• Published in: Journal of physics. Condensed matter 2012-09, Vol.24 (36), p.1-12
• Main Authors: Barzola-Quiquia, J, Lessig, A, Ballestar, A, Zandalazini, C, Bridoux, G, Bern, F, Esquinazi, P
• Format: Article
• Language: English
• Subjects: Anisotropy; Bias; Condensed matter; Exchange; Ferromagnetic materials; Magnetization; Magnetoresistance; Magnetoresistivity
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/24/36/366006

We have investigated exchange bias effects in bilayers composed of the antiferromagnetic o-YMnO sub(3) and ferromagnetic Co thin film by means of SQUID magnetometry, magnetoresistance, anisotropic magnetoresistance and the planar Hall effect. The magnetization and magneto-transport properties show pronounced asymmetries in the field and magnetization axes of the field hysteresis loops. Both exchange bias parameters, the exchange bias field H sub(E)T)as well as the magnetization shift M sub(E)T) vanish around the Neel temperature T sub(N) [Asymptotically = to] 45 K. We show that the magnetization shift M sub([)Sigma]T)is also measured by a shift in the anisotropic magnetoresistance and planar Hall resistance having a similar temperature dependence as the one obtained from magnetization measurements. Because the o-YMnO sub(3) film is highly insulating, our results demonstrate that the M sub(E)T)shift originates at the interface within the ferromagnetic Co layer. To show that the main results obtained are general and not because of some special characteristics of the o-YMO sub(3) layer, similar measurements were done in Co/CoO micro-wires. The transport and magnetization characterization of the micro-wires supports the main conclusion that these effects are related to the response of the ferromagnetic Co layer at the interface.