5d transition metal Pt is the canonical spin Hall material for efficient generation of spin-orbit torques (SOTs) in Pt/ferromagnetic layer (FM) heterostructures. However, for a long while with tremendous engineering endeavors, the damping-like SOT efficiencies (${ \xi}_{ DL}$) of Pt and Pt alloys have still been limited to ${ \xi}_{ DL}$<0.5. Here we present that with proper alloying elements, particularly 3d transition metals V and Cr, a high spin-orbital Hall conductivity (${ \sigma}_{ SH}{ \sim}6.5{ \times}10^{ 5}({ \hbar}/2e){ \Omega}^{ -1}{ \cdot} m^{ -1}$) can be developed. Especially for the Cr-doped case, an extremely high ${ \xi}_{ DL}{ \sim}0.9$ in a Pt$_{ 0.69}$Cr$_{ 0.31}$/Co device can be achieved with a moderate Pt$_{ 0.69}$Cr$_{ 0.31}$ resistivity of ${ \rho}_{ xx}{ \sim}133 { \mu}{ \Omega}{ \cdot}cm$. A low critical SOT-driven switching current density of $J_{ c}{ \sim}3.2{ \times}10^{ 6} A{ \cdot}cm^{ -2}$ is also demonstrated. The damping constant (${ \alpha}$) of Pt$_{ 0.69}$Cr$_{ 0.31}$/FM structure is also found to be reduced to 0.052 from the pure Pt/FM case of 0.078. The overall high ${ \sigma}_{ SH}$, giant ${ \xi}_{ DL}$, moderate ${ \rho}_{ xx}$, and reduced ${ \alpha}$ of such a Pt-Cr/FM heterostructure makes it promising for versatile extremely low power consumption SOT memory applications.
Categories: cond-mat.mtrl-sci