Spin Hall Magnetoresistance of a Heavy Metal - Ferrimagnet Heterostructure

Metallic amorphous ferrimagnetic alloys of 3d transition metals (TM) and 4f lanthanides (Ln) exhibit interesting magnetic behavior due to the interplay between the 3d and 4f magnetic sublattices. Tuning TM and Ln concentrations can effectively modulate the compensation temperature and further extend it to room temperature. In recent years, the heterostructures of these ferrimagnetic films with heavy metals possessing strong spin-orbit coupling have gained intensive attention for their potential use in nonvolatile memory devices. Here, we have investigated the anomalous Hall resistivity (ρ_xy^AHE ) spin Hall magnetoresistance (SHMR) and dc magnetization of Pt /Co_1-xHo_x /Al, Ti/Co_1-xHo_x/Al and Co_1-xHo_x/Al deposited using multitarget magnetron sputtering. The ρ_xy^AHE shows unusual triple hysteresis loops just below the compensation temperature (T_comp) which disappears at lower temperatures. In addition to a lack of triple hysteresis loops, the ρ_xy^AHE above T_comp also features a sign reversal. The SHMR of these samples has been measured over a wide field range across the compensation temperature, together with imaging of magnetic textures with magnetic force microscopy and magneto-optic Kerr effect (MOKE) microscopy at room temperature. The use of Brillouin light scattering microscopy to probe magnons and the effect of chiral exchange at the Pt/CoHo interface is in progress. Results of these measurements will be presented in detail at the meeting.