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

Cornell Affiliated Author(s)

Author

Isaiah Gray
Gregory Stiehl
John Heron
Antonio Mei
Darrell Schlom
Ramamoorthy Ramesh
Daniel Ralph
Gregory Fuchs

Abstract

Uncompensated moments (UMs) 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 magnetothermal microscopy to image micron-scale uncompensated moments in thin films of FeRh, a room-temperature antiferromagnet that exhibits a first-order phase transition to a ferromagnetic (FM) state near 400 K. FeRh provides the unique opportunity to study both uncompensated moments in the antiferromagnetic (AF) phase and the interaction of uncompensated moments with emergent ferromagnetism within a relatively broad (390-420 K) temperature range near TC. In the AF phase below TC, 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 TC, 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 FM domains are pinned in different in-plane orientations, even in the presence of a nominally saturating magnetic field, before suddenly collapsing into a state uniformly parallel to the field. © 2019 American Physical Society.

Date Published

Journal

American Physical Society (APS)

Volume

3

Issue

12

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077342768&doi=10.1103%2fPhysRevMaterials.3.124407&partnerID=40&md5=a8209527b2eac8bf53cd1db3eaa8cc46

DOI

10.1103/PhysRevMaterials.3.124407

Funding Source

1542081
1708499
1719875
1740136
SRC

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