BiFeO_3/Ni_(81)Fe_(19)磁性双层膜中的交换偏置及其热稳定性研究

Exchange bias in BiFeO_3 /Ni_(81) Fe_(19) magnetic films and its thermal stability

研究了磁场诱导生长的BiFeO3/Ni18Fe19磁性双层膜中的交换偏置及其热稳定性.结果表明:BiFeO3/Ni18Fe19双层膜中的交换偏置场Hex未表现出明显的磁练习效应.在负饱和磁场等待过程中,BiFeO3/Ni18Fe19双层膜磁滞回线的前支和后支曲线都随着在负饱和磁场中等待时间tsat的增加向正场方向偏移.交换偏置场Hex的大小随着等待时间tsat的增加而减小,矫顽力Hc基本不变.交换偏置场Hex的大小随测量温度Tm的升高变化不明显,表现出良好的热稳定性;但矫顽力Hc随Tm的升高而显著减小.良好的热稳定性应该来源于铁电性和反铁磁性间的共同耦合作用.

This paper deals with the exchange bias and its thermal stability in magnetic BiFeO 3 / Ni 81 Fe 19 bilayer sputtered under an electromagnetic field. The results show that the BiFeO 3 /Ni 18 Fe 19 bilayer presents an in-plane uniaxial magnetic anisotropy and a significant exchange bias effect, however the exchange bias field H ex in the BiFeO 3 /Ni 18 Fe 19 bilayer does not show a visible training effect. The forward and recoil loop shifts towards positive fields, while holding the film in a negative saturation field. H ex decreases monotonously with the increase in the holding time （tsat ）, whereas H c is almost the same. With increasing temperature T m , H ex will not alter significantly, which means that H ex is not sensitive to the temperature, showing a good thermal stability. However, H c may reduce rapidly with the increase in temperature. We believe that the good thermal stability may result from the coupling between ferroelectric and antiferromagnetic moments in BiFeO 3 .