Imaging uncompensated moments and exchange-biased emergent ferromagnetism in FeRh thin films

Abstract

Uncompensated moments in antiferromagnets are responsible for exchange bias in antiferromagnet/ferromagnet heterostructures; however, they are difficult to directly detect because any signal they contribute is typically overwhelmed by the ferromagnetic layer. We use magneto-thermal microscopy to image uncompensated moments in thin films of FeRh, a room-temperature antiferromagnet that exhibits a 1st-order phase transition to a ferromagnetic state near 100~${}^{\circ }$C. FeRh provides the unique opportunity to study both uncompensated moments in the antiferromagnetic phase and the interaction of uncompensated moments with emergent ferromagnetism within a relatively broad (10-15~${}^{\circ }$C) temperature range near $T_C$. In the AF phase below $T_C$, we image both pinned UMs, which cause local vertical exchange bias, and unpinned UMs, which exhibit an enhanced coercive field that reflects exchange-coupling to the AF bulk. Near $T_C$, where AF and FM order coexist, we find that the emergent FM order is exchange-coupled to the bulk Néel order. This exchange coupling leads to the nucleation of unusual configurations in which different FM domains are pinned parallel, antiparallel, and perpendicular to the applied magnetic field before suddenly collapsing into a state uniformly parallel to the field.

arXiv comment29 pages and 16 figures with appendix

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Cited by in corpus (6)

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• Local Photothermal Control of Phase Transitions for On-demand Room-temperature Rewritable Magnetic Patterning
• Magnetic imaging and statistical analysis of the metamagnetic phase transition of FeRh with electron spins in diamond
• Phase Boundary Exchange Coupling in the Mixed Magnetic Phase Regime of a Pd-doped FeRh Epilayer
• Nanoscale magnetization and current imaging using scanning-probe magneto-thermal microscopy