Experimental Investigation of the Nature of the Magnetoresistance Effects in Pd-YIG Hybrid Structures

In bilayers consisting of Pd and yttrium iron garnet (${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ or YIG), we observe vanishingly small room-temperature conventional anisotropic magnetoresistance but large new magnetoresistance that is similar to the spin Hall magnetoresistance previously reported in Pt-YIG bilayers. We report a temperature dependence study of the two magnetoresistance effects in Pt-YIG bilayers. As the temperature is decreased, the new magnetoresistance shows a peak, whereas the anisotropic magnetoresistance effect starts to appear and increases monotonically. We find that the magnetoresistance peak shifts to lower temperatures in thicker Pd samples, a feature characteristic of the spin current effect. The distinct temperature dependence reveals fundamentally different mechanisms responsible for the two effects in such hybrid structures.

Figure 1

(a) AFM image of a representative YIG thin film. Inset: Line scan across the terraces (along the arrow direction). (b) Normalized magnetic hysteresis loops at 300 K of a YIG-GGG film with an applied field in-plane (${\mathrm{H}}_{\parallel }$) and out-of-plane (${\mathrm{H}}_{\perp }$). Inset: FMR spectrum of a bare 30 nm thick YIG on GGG.

Figure 2

(a) Schematic diagram of the patterned Hall bar and notations for different field rotations. (b) and (c) show typical field rotation magnetoresistance data with $\mathrm{H}=10\mathrm{kOe}$ in three orthogonal planes for $\mathrm{Pd}(2\mathrm{nm})\text{−}\mathrm{YIG}(30\mathrm{nm})$ at 100 K (b) and 3 K (c).

Figure 3

Magnetoresistance data for $\mathrm{Pd}(2\mathrm{nm})\text{−}\mathrm{YIG}(30\mathrm{nm})$ with $\mathrm{H}=10\mathrm{kOe}$ at different temperatures for $\alpha$ sweeps (a), $\beta$ sweeps (b), and $\gamma$ sweeps (c). (d) Temperature dependence of the magnetoresistance oscillation amplitude in all three rotational configurations. $\alpha$-, $\beta$- and $\gamma$-sweeps represent AMR, SMR, and $\mathrm{AMR}+\mathrm{SMR}$, respectively. “$\mathrm{AMR}+\mathrm{SMR}$ (exp.)” is the amplitude of the magnetoresistance oscillations measured in the $\gamma$ sweep, and “$\mathrm{AMR}+\mathrm{SMR}$ (calc.)” is the sum of two amplitudes in the $\alpha$ and $\beta$ sweeps.

Figure 4

SMR measured in the $\beta$ sweeps as a function of temperatures for three different Pd layer thicknesses: 2, 3, and 4 nm. Inset: SMR vs $\mathit{d}/\lambda$ calculated using Eq. (2).