Spin transport through a nanojunction with a precessing anisotropic molecular spin -- Gilbert damping and spin-transfer torque (2412.06586v1)

Abstract: The subject of this study is spin transport through an orbital belonging to a magnetic molecule, connected to two leads, and coupled via exchange interaction with the precessing anisotropic molecular spin in a constant magnetic field. The expressions for spin current components, noise of $z$-polarized spin current, spin-transfer torque, Gilbert damping and other torque coefficients are obtained using the Keldysh nonequilibrium Green's functions technique. The precession of the molecular spin, and hence, the inelastic tunnelling processes involving spin-flip events between molecular quasienergy levels, driven by this precession, can be controlled by the uniaxial magnetic anisotropy parameter. By setting the Larmor precession frequency, the tilt angle of molecular magnetization with respect to the magnetic field, and the magnetic anisotropy parameter, one can modulate the spin-current components and noise, spin-transfer torque and related torque coefficients. Moreover, the dc-spin current and spin-transfer torque components provide the quasienergy level structure in the orbital and the torque vanishes for a suppressed molecular spin precession, obtained by proper adjustment of the anisotropy parameter and magnetic field, allowing to reveal the anisotropy parameter via a dc-spin current or torque measurement. The results of the study show that spin transport and spin-transfer torque generated on the anisotropic molecular spin can be manipulated by the uniaxial anisotropy parameter of the molecular spin even in the absence of the magnetic field.