Transport Magnetic Proximity Effects in Platinum

Platinum (Pt) metal, being nonmagnetic and with a strong spin-orbit coupling interaction, has been central in detecting the pure spin current and establishing most of the recent spin-based phenomena. Magnetotransport measurements, both electrical and thermal, conclusively show strong ferromagnetic characteristics in thin Pt films on the ferromagnetic insulator due to the magnetic proximity effects. The pure spin current phenomena measured by Pt, including the inverse spin Hall and the spin Seebeck effects, are thus contaminated and not exclusively established.

Figure 1

(a) Normalized magnetic hysteresis loop at 300 K of the YIG substrate as a function of magnetic field $H$ applied in-plane along the long axis ($H_{\parallel }$), short axis ($H_T$), and perpendicular to plane ($H_{\perp }$). (b) Schematic diagram of the patterned Hall bar on a substrate in the $xy$ plane with $H$ at angle $\theta$. Contacts for transport and thermal measurements are labeled in numbers. (c) Schematic diagram of multiple patterned strips in ascending thickness.

Figure 2

(a) MR measurement (left scale) of $\mathrm{Pt}(14\mathrm{nm})/\mathrm{YIG}$, $\mathrm{Cu}(10\mathrm{nm})/\mathrm{YIG}$, and $\mathrm{Pt}(10\mathrm{nm})/\mathrm{Si}$ as a function of magnetic field $H$ at $\theta =0°({\rho }_{\parallel })$ and $90°({\rho }_T)$. Also shown is the normalized magnetization curve (right scale) of $\mathrm{Pt}(14\mathrm{nm})/\mathrm{YIG}$ at $\theta =0°(M_x)$ and $90°(M_y)$. (b) MR results (left scale) of ${\rho }_{\parallel }$ and ${\rho }_T$ and field-dependent thermal voltages (right scale) at $\theta =0°(V_{36}{)}_{\mathrm{th}}$ and $90°(V_{12}{)}_{\mathrm{th}}$ of $\mathrm{Py}(10\mathrm{nm})/\mathrm{YIG}$. (c) MR results of ${\rho }_{\parallel }$ and ${\rho }_T$ of $\mathrm{Py}(50\mathrm{nm})/\mathrm{Si}$. (d) AMR ratio as a function of the metal layer thickness $t$ of $\mathrm{Pt}/\mathrm{YIG}$ (open triangles and squares for polycrystalline and single crystal YIG) and $\mathrm{Py}/\mathrm{YIG}$ (blue open circles for polycrystalline YIG). Lines are guides to the eyes.

Figure 3

Field dependence of Hall resistance $R_H$ at different temperatures for (a) $\mathrm{Cu}(10\mathrm{nm})/\mathrm{YIG}$ and $\mathrm{Pt}(15\mathrm{nm})/\mathrm{Si}$ and (b) $\mathrm{Pt}(10\mathrm{nm})/\mathrm{YIG}$ (single crystal YIG). The inset shows the carrier concentration as a function of the temperature for $\mathrm{Pt}(10\mathrm{nm})/\mathrm{YIG}$, $\mathrm{Pt}(15\mathrm{nm})/\mathrm{Si}$, and $\mathrm{Cu}(10\mathrm{nm})/\mathrm{YIG}$. (c) The anomalous Hall coefficient $R_{\mathrm{AHE}}$ as a function of the temperature for $\mathrm{Pt}(10\mathrm{nm})/\mathrm{YIG}$. Lines are guides to the eyes. The inset shows anomalous Hall coefficient $R_{\mathrm{AHE}}$ as a function of magnetic field.

Figure 4

(a) Field-dependent thermal voltage $(V_{12}{)}_{\mathrm{th}}$ for $\mathrm{Pt}(10\mathrm{nm})/\mathrm{YIG}$ at a different angle $\theta$. (b) MR results (right scale, ${\rho }_{\parallel }$ and ${\rho }_T$) of $\mathrm{Pt}(10\mathrm{nm})/\mathrm{YIG}$ and thermal voltages [left scale, $(V_{36}{)}_{\mathrm{th}}$ and $(V_{12}{)}_{\mathrm{th}}$] of $\mathrm{Pt}(10\mathrm{nm})/\mathrm{YIG}$, $\mathrm{Pt}(15\mathrm{nm})/\mathrm{Si}$, and $\mathrm{Cu}(10\mathrm{nm})/\mathrm{YIG}$. (c) Linear dependence of thermal voltages $(V_{12}{)}_{\mathrm{th}}$ and $(V_{36}{)}_{\mathrm{th}}$ on heating power. The inset shows angular dependence of thermal voltage $(V_{12}{)}_{\mathrm{th}}$ following $\sin \theta$. (d) Thermal voltage from multiple strips [Fig. 1c] as a function of Pt and Py thicknesses. Lines are guides to the eyes.