Enhanced B2 Ordering of FeRh Thin Films Using B2 NiAl Underlayers

B2-ordered FeRh thin films undergo a first-order magnetic transition from an antiferromagnetic (AFM) state at low temperature to a ferromagnetic (FM) state above 350 K and reverse back on cooling with a finite hysteresis. This property makes them very attractive for use in temperature-controlled exchange coupling layers for heat-assisted magnetic recording. In order to be used as an exchange coupling layer, the goal is to fabricate ultra-thin films of FeRh that show reversible AFM-FM switching. For thinner films grown on MgO substrates, there exists an FM signal below the AFM-FM transition temperature. It is demonstrated that there is a direct correlation between the low-temperature FM fraction and the extent of atomic ordering. Based on this observation, the enhanced atomic order in FeRh grown on NiAl underlayers is shown to result in bulk-like AFM-FM switching, especially for the thinner films.

B2有序的FeRh薄膜在低温下从反铁磁（AFM）态经历一阶磁相变到350 K以上的铁磁（FM）态，并且在冷却时以有限的磁滞回线变回反铁磁态。这一特性使其在热辅助磁记录的温控交换耦合层中极具应用吸引力。为了用作交换耦合层，目标是制备出显示可逆的AFM - FM转换的超薄FeRh薄膜。对于在MgO衬底上生长的更薄的薄膜，在AFM - FM转变温度以下存在一个FM信号。研究表明，低温下的FM成分与原子有序程度之间存在直接关联。基于这一观察结果，发现在NiAl底层上生长的FeRh中增强的原子有序性会导致类似体材料的AFM - FM转换，尤其是对于更薄的薄膜。