Heterostructures*

The antiferromagnetic coupling between 4f and 3d spin sublattices in amorphous films of GdFeCo alloys is known to affect the temperature dependence of magnetization and magnetic anisotropy dramatically. Multilayers of these alloys also reveal non-trivial spin textures driven by dipolar and chiral exchange interactions. Here we present measurements of anomalous Hall (AH) and planar Hall (PH) voltages in β -W/Gd_x(Fe_yCo_1-y)_1-x bilayer films across the sublattice magnetization compensation point and the temperature at which the magnetic anisotropy changes from in-plane to out-of-plane configuration. We observe a robust planar Hall Effect in these samples that tracks the behavior of magnetization measured with vibrating sample magnetometry. The magnetization switching fields extracted from the PH data allow calculations of anisotropy energy as a function of temperature and 4f/3d moment ratios in the films. The anomalous Hall data in the reversible and irreversible regimes of response are analyzed to extract the Berry phase and spin orbit torque contributions to Hall resistivity.