Origins of anomalous Hall effect in heavy metal/ferrimagnetic insulator with perpendicular magnetic anisotropy.

Ferrimagnetic insulators are promising for low-power and high-speed spintronic applications. Here, we use temperature dependent Hall measurements to identify contributions of spin Hall, magnetic proximity, and sublattice effects to the anomalous Hall signal in heavy metal/ferrimagnetic insulator heterostructures with perpendicular magnetic anisotropy. This approach enables detection of both the magnetic proximity effect onset temperature and magnetization compensation temperature and provides essential information regarding the interfacial exchange coupling. Onset of a magnetic proximity effect yields a local extremum in the temperature dependent anomalous Hall signal, which occurs at higher temperature as ferrimagnetic insulator thickness increases. This proximity effect onset occurs at much higher temperature in Pt than W. In contrast, the magnetization compensation point is identified by a sharp anomalous Hall effect sign change and divergent coercive field. We confirm our observations using X-ray magnetic circular dichroism and polarized neutron reflectometry, which directly probe the magnetic proximity effect and interface exchange coupling configuration, helping define the anomalous Hall effect sign of the magnetized heavy metal.