Abstract
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.
Highlights
An important device in spintronics is the magnetic tunnel junction (MTJ), which is coupled with two electrodes via quantum tunneling
The tunnel magnetoresistance (TMR) up to about 1800% was approached in the MTJ at low temperatures3 with La0.7Sr0.3MnO3(LSMO) electrodes and SrTiO3(STO) tunnel barrier
The high rates of tunneling anisotropic magnetoresistance (TAMR) and spin polarized current are realized with the FM dimer tunnel junction, which can be used as a functional device in the technical applications
Summary
An important device in spintronics is the magnetic tunnel junction (MTJ), which is coupled with two electrodes via quantum tunneling. Using the spin coherent state representation of the tunneling spin, the interface density of states can be formulated for the non-collinear magnetization of electrode with respect to the anisotropy axis of the molecule dimer. The non-collinear magnetization of FM electrode with respect to the anisotropy easy axis results in the angle dependence of the tunneling rate of spin- ↑ and spin- ↓ electrons. To this end we begin with the spin coherent states of spinprojection operator σ ⋅ n, such that σ⋅n ±n⟩ = ± ±n⟩. The non-collinear spin projection operator σ ⋅ n with respect to the anisotropy easy-axis of molecule dimer may serve as the effective SOC in the usual MTJ system.. The non-collinear spin projection operator σ ⋅ n with respect to the anisotropy easy-axis of molecule dimer may serve as the effective SOC in the usual MTJ system. The tunneling electron experiences an exchange coupling with the localized non-collinear magnetic moments.
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