Min-Han Lee https://orcid.org/0000-0001-9093-4891
Kirill D. Belashchenko https://orcid.org/0000-0002-8518-1490
Ivan K. Schuller https://orcid.org/0000-0002-9078-7120
Date of this Version
PHYSICAL REVIEW B 102, 174406 (2020)
We have probed directly the temperature and magnetic field dependence of pinned uncompensated magnetization at the interface of antiferromagnetic FeF2 with Cu, using FeF2-Cu-Co spin valves. Electrons polarized by the Co layer are scattered by the pinned uncompensated moments at the FeF2-Cu interface giving rise to giant magnetoresistance. We determined the direction and magnitude of the pinned uncompensated magnetization at different magnetic fields and temperatures using the angular dependencies of resistance. The strong FeF2 anisotropy pins the uncompensated magnetization along the easy axis independent of the cooling field orientation. Most interestingly, magnetic fields as high as 90 kOe cannot break the pinning at the FeF2-Cu interface. This proves that the pinned interfacial magnetization is strongly coupled to the antiferromagnetic order inside the bulk FeF2 layer. Studies as a function of FeF2 crystalline orientation show that uncompensated spins are only detected in a spin valve with (110) crystal orientation, but not in valves containing FeF2(100) and FeF2(001). This observation is in agreement with symmetry-related considerations which predict the equilibrium boundary magnetization for the FeF2(110) layer.
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