Effect of uniaxial magnetic anisotropy on charge transport in a junction with a precessing anisotropic molecular spin

Abstract: Anisotropic molecular magnets can be employed to manipulate charge transport in molecular nanojunctions. The charge transport through an electronic level connected to source and drain metallic contacts and exchange-coupled with a precessing anisotropic molecular spin in a constant external magnetic field is studied here. Both the magnetic field and the uniaxial magnetic anisotropy parameter of the molecular spin control the total precession frequency. The Keldysh nonequilibrium Green's functions method is used to derive expressions for charge current and current noise. The precessing molecular magnetization drives inelastic tunnelling processes between electronic quasienergy levels. The dc-bias voltages allow to unveil the quasienergy levels, Larmor frequency and the anisotropy parameter, through characteristics of charge-transport measurements involving features such as steps, peaks and dips. Under zero-bias voltage conditions, for a sufficiently large anisotropy parameter that enables the decrease of the total precession frequency or change of the precession direction with respect to Larmor precession, the shot noise is reduced. Furthermore, it is possible to adjust the magnetic anisotropy parameter to suppress the precession frequency, leading to the suppression of shot noise. The results show that in the given setup, the charge current and shot noise can be controlled by the uniaxial magnetic anisotropy of the molecular magnet.