Magnetism of mass-selected FeRh B2 nanocrystals in epitaxy on perovskite oxide

Near equiatomic composition, FeRh bulk alloys exhibit a CsCl-type (B2) chemically ordered phase related to a metamagnetic transition from an antiferromagnetic (AFM) to a ferromagnetic (FM) state close to ambient. Recently, we underlined the main role of Rh atoms on the metamagnetic transition for samples with high-density FeRh nanoparticles assemblies, where Rh kept a residual FM signature even at low temperature. The objective of this proposal is to study low-density samples, of mass-selected FeRh nanoparticles (NPs) grown on perovskite oxide, from X-ray absorption spectroscopy and magnetic circular dichroism (XAS/XMCD) experiments at Fe K and Rh L-edges at ID12 to explore interfacial strain effects on the magnetic order of epitaxial FeRh nanoparticles. Both use of quarter-wave plate to enhance the circular polarization rate and SDD with appropriate energy filter mounted in the 8T-cryomagnet would improve the signal to noise ratio in such diluted hybrid-nanostructures.

具有近等原子比的FeRh块体合金，存在与室温附近反铁磁（antiferromagnetic, AFM）到铁磁（ferromagnetic, FM）的变磁转变相关的CsCl型（B2）化学有序相。此前我们针对高密度FeRh纳米颗粒组装体样品，阐明了Rh原子在变磁转变中的核心作用：即便在低温下，这类样品中的Rh仍保留有残留铁磁特征。本项目旨在研究生长于钙钛矿氧化物上的质量筛选型FeRh纳米颗粒（NPs）低密度样品，通过在ID12光束线开展Fe K边与Rh L边的X射线吸收谱与磁圆二色谱（XAS/XMCD）实验，探究界面应变对外延FeRh纳米颗粒磁有序的影响。实验中，采用四分之一波片（quarter-wave plate）提升圆偏振率，并在8特斯拉低温磁体（8T-cryomagnet）中搭载配备适配能量滤波器的硅漂移探测器（SDD），可有效改善这类稀释型杂化纳米结构的信噪比。