钉扎未补偿磁矩对柔性衬底上铁磁/反铁磁薄膜交换偏置的影响

Effect of pinned uncompensated moments on the exchange bias offerromagnetic/antiferromagnetic film on flexible substrates

目的:旨在确定柔性衬底上对交换偏置的主要贡献是铁磁(FM)/反铁磁(AFM)界面效应还是AFM体效应。方法:采用超高真空磁控溅射法在柔性衬底PI上制备Ni_(81)Fe_(19)/Fe_(50) Mn_(50)双层膜和Ni_(81)Fe_(19)/Fe_(50)Mn_(50)/Ni_(81)Fe_(19)三层膜,将其退火后使用振动样品磁强计测试样品的场冷磁滞回线,分别研究了交换偏置场与顶层FM层厚度、AFM层厚度和底层FM层厚度之间的关系。结果:三层膜交换偏置场的数值远小于双层膜的;交换偏置场随顶部和底部Ni_(81)Fe_(19)层厚度的变化呈现相同规律,均随层厚增大而减小;交换偏置场随AFM层厚度的增大出现先为零随后快速增大到最大值然后有所下降后保持不变。结论:在Ni_(81)Fe_(19)/Fe_(50)Mn_(50)/Ni_(81)Fe_(19)三层膜中,两个FM层共享AFM层或AFM层的磁重序,从而减少AFM层的有效钉扎未补偿磁矩,导致交换偏置场降低。

Aims:The purpose of this paper is to determine whether the main contribution to the exchange bias on flexible substrates is the ferromagnetic(FM)/antiferromagnetic(AFM)interface effect or the AFM bulk effect.Methods:The Ni_(81)Fe_(19)/Fe_(50)Mn_(50) bilayers and Ni_(81)Fe_(19)/Fe_(50)Mn_(50)/Ni_(81)Fe_(19) trilayers were prepared by the ultra-high vacuum magnetron sputtering method on the flexible substrate PI;and the hysteresis loop of the sample was tested by the vibration sample magnetometer after annealing.The relationship between the exchange bias field and the top FM thickness and the ralationship between the AFM layer thickness and the bottom FM layer thickness were studied respectively.Results:It was found that the value of the exchange bias field of the three-layer film was much smaller than that of the double-layer film.The exchange bias field showed the same rule with the thickness of the Ni_(81)Fe_(19) layer at the top and bottom and decreased with the increase of the layer thickness.With the increase of the AFM layer thickness,the exchange bias field first reached zero,then increased rapidly to the maximum,then decreased again and finally remained unchanged.Conclusions:In the Ni_(81)Fe_(19)/Fe_(50)Mn_(50)/Ni_(81) Fe_(19) trilayers,the two FM layers share the AFM layer or the AFM layer s magnetic reorder,thus reducing the effective pinning uncompensated magnetic moment of the AFM layer,resulting in a decrease in the exchange bias field.