NiFe/FeMn双层膜交换偏置的形成及热稳定性研究

The establishment and thermal stability of exchange bias in NiFe/FeMn bilayers

研究了在铁磁 (NiFe) 反铁磁 (FeMn)双层膜之间 ,交换偏置的形成过程和热稳定性 ,特别是NiFe FeMn的交换偏置作用与FeMn层晶粒尺寸的关系 .和以前作者不同的是 ,本文方法采用非磁性Ni Fe Cr合金作缓冲层材料 ,改变Cr的含量就可以获得不同晶粒尺寸的反铁磁FeMn层 .实验表明 ,晶粒尺寸较小的FeMn产生较强的铁磁 反铁磁交换偏置场 ;但是 ,对于较大晶粒的FeMn层 ,出现交换偏置作用所要的临界厚度较小 .这符合Mauri提出的理论模型 .交换偏置场的热稳定性实验表明 ,具有较大晶粒尺寸的FeMn层给出较高的偏置场的截止温度 .这和Noshioka的实验与理论一致 ,即较大的反铁磁层晶粒具有较大的激活能和较长的弛豫时间 .

The establishment and thermal stability of exchange bias between the ferromagnetic NiFe layer and antiferromagnetic FeMn layer have been studied. We focused on the relationship between FeMn grain size and exchange bias with the size of FeMn grains controlled by varying Cr content in Ni-Fe-Cr alloy buffer layer. The results indicate that, smaller FeMn grains lead to a larger exchange bias field, but the thickness with the exchange bias setting on is larger, which is consistent with Mauri's model. Thermal stability of the exchange bias indicates that, the films with bigger FeMn grains have a higher blocking temperature, which is in agreement with Noshioka's conclusion: bigger antiferromagnetic grains possess higher activation energies and longer relaxation times.