https://doi.org/10.1140/epjb/e2013-31003-y
Regular Article
Temperature dependent exchange bias effect in polycrystalline BiFeO3/FM (FM = NiFe, Co) bilayers
1 National Laboratory of Solid State
Microstructures and Department of Physics, Nanjing University,
Nanjing
210093, P.R.
China
2 Department of Physics, Southeast
University, Nanjing
211189, P.R.
China
3 Department of Physics, Tongji
University, Shanghai
200092, P.R.
China
a e-mail: xuqingyu@seu.edu.cn
b e-mail: jdu@nju.edu.cn
Received:
3
November
2012
Received in final form:
23
January
2013
Published online:
27
March
2013
Extensive studies on the temperature (T) dependent exchange bias effect were carried out in polycrystalline BiFeO3(BFO)/NiFe and BFO/Co bilayers. In contrast to single-crystalline BFO/ferromagnet (FM) bilayers, sharp increase of the exchange bias field (HE) below 50 K were clearly observed in both of these two bilayers. However, when T is higher than 50 K, HE increases with T and decreases further when T is larger than 230 K (for BFO/NiFe) or 200 K (for BFO/Co), which is similar to those reported in single-crystalline BFO/FM bilayers. After the exploration of magnetic field cooling, the temperature dependent exchange bias can be explained considering two contributions from both the interfacial spin-glass-like frustrated spins and the polycrystalline grains in the BFO layer. Moreover, obvious exchange bias training effect can be observed at both 5 K and room temperature and the corresponding results can be well fitted based on a recently proposed theoretical model taking into account the energy dissipation of the AFM layer.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2013