Pt Magnetic Polarization on ${\mathbf{Y}}_3{\mathrm{Fe}}_5{\mathbf{O}}_{12}$ and Magnetotransport Characteristics

Thin Pt films on an yttrium iron garnet ($\mathrm{YIG}={\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$) show ferromagneticlike transport properties, which may impact the functionality of Pt in spin current detection, but do not provide direct quantitative information on the Pt magnetization. We report magnetic x-ray magnetic circular dichroism measurements of $\mathrm{YIG}/\mathrm{Pt}(1.5\mathrm{nm})$ showing an average Pt moment of $0.054{\mu }_{\mathrm{B}}$ at 300 K and $0.076{\mu }_{\mathrm{B}}$ at 20 K. This observation indicates strong proximity effects and induced magnetic ordering in Pt on magnetic insulators and their contribution to the spin-related measurements should not be neglected. The transport characteristics also suggest considerable modifications in the Pt electronic structure due to magnetic ordering.

Figure 1

(a) Atomic force microscopy surface topography of a representative YIG film and (b) corresponding room temperature in-plane and perpendicular $M\mathrm{\text{−}}H$ curves. The inset shows the temperature dependence of the YIG spontaneous magnetization.

Figure 2

(a) Normalized synchrotron x-ray absorption spectra, and (b) corresponding x-ray magnetic dichroism with an in-plane magnetic field of $\pm 500\mathrm{Oe}$ from the $\mathrm{YIG}/\mathrm{Pt}(1.5\mathrm{nm})$ at 300 and 20 K. Inset compares the first derivative of the XAS spectra with the XMCD signal of $L_3$ edge obtained at 20 K. Error bars are included in the XMCD results to indicate measurement noise level.

Figure 3

(a) Longitudinal and transverse MR curves of a $\mathrm{YIG}/\mathrm{Pt}(1.5\mathrm{nm})$ sample measured at 300 and 5 K with electrode configuration shown in the inset; (b) and (c) coupled MR and Nernst effect measurements for a $\mathrm{YIG}/\mathrm{Pt}(4.0\mathrm{nm})$ sample; and (d) Pt thickness dependence of AMR ratio for $\mathrm{YIG}/\mathrm{Pt}$ at 300 and 5 K. The solid lines are guides for the eye. Inset in (d) plots the resistivity as a function of in-plane field direction (8 kOe) for a representative sample $\mathrm{YIG}/\mathrm{Pt}(1.5\mathrm{nm})$ at 300 K, and the solid line is a fitting result using cosine square function.

Figure 4

(a) Temperature dependence of the anisotropic magnetoresistance for a $\mathrm{YIG}/\mathrm{Pt}(1.5\mathrm{nm})$ and a $\mathrm{YIG}/\mathrm{Pt}(4\mathrm{nm})$ film. (b) Comparison of the thickness dependent Pt thin film resistivity grown on YIG and GGG substrates as a function of temperature; and (c) ordinary Hall coefficient measured for Pt films grown on YIG and GGG substrates.