Quantum simulation of ferromagnetic and anti-ferromagnetic tunneling anisotropic magnetoresistance in a single-molecule-magnet dimer tunnel-junction

In this work, we simulate the tunneling anisotropic magnetoresistance (TAMR) in a single-molecule-magnet (SMM) dimer tunnel-junction with metal and ferromagnetic (FM) electrodes. The non-collinear polarization of electrode with respect to the uniaxial anisotropy-axis of magnet results in both the FM and anti-ferromagnetic (AFM) TAMR respectively for the FM and AFM inter-molecule couplings. In terms of the spin coherent state representation of electron spin the non-collinear tunneling is able to be analyzed with the usual rate equation approach in a sequential tunneling regime. The ferromagnetic TAMR varies with the non-collinear angle and the tunneling magnetoresistance (TMR) is just a special case of the angle θ = π. With the FM dimer we obtain the higher TMR up to 400% and the high polarization rate (79%) of spin current as well. The angle dependence of TAMR for the AFM dimer is also presented along with the spin current.