Toward 100% Spin-Orbit Torque Efficiency with High Spin-Orbital Hall Conductivity Pt-Cr Alloys

5d transition metal Pt is the canonical spin Hall material for efficient generation of spin-orbit torques (SOTs) in Pt/ferromagnetic layer (FM) hetero-structures. 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) approximate to 6.5 x 10(5) (h/2e) Omega(-1) m(-1)) can be developed. Especially for the Cr-doped case, an extremely high xi(DL) approximate to 0.9 in a Pt0.69Cr0.31/Co device can be achieved with a moderate Pt0.69Cr0.31 resistivity of rho(xx) approximate to 133 mu Omega cm. A low critical SOT-driven switching current density of J(c) approximate to 3.2 x 10(6) A cm(-2) is also demonstrated. The damping constant (a) of the Pt0.69Cr0.31/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 a of such a Pt-Cr/FM heterostructure makes it promising for versatile extremely low power consumption SOT memory applications.

Automated summary

The development of high spin-orbital Hall conductivity, giant damping-like SOT efficiency, and low power consumption SOT memory devices can be achieved through proper alloying.