Realization of extreme tunnel magnetoresistance with a molecule-magnet-dimer junction

Abstract

By means of the Rate equation approach in the sequential tunneling regime, we study spin-polarized transport through a molecule magnet dimer of both ferromagnetic (FM) and antiferromagnetic (AFM) types, which is weakly coupled to collinear FM leads. We pay particular attention to the effect of spin exchange interactions between electron spin and the molecule magnet on the tunnel magnetoresistance (TMR). Giant positive TMR is found in the positive bias with the AFM dimer.Particularly we are able to realize the negative TMR of theoretical lowest limit. And thus the molecule dimer device acts as an ideal valve to blockade completely the current channel of parallel configuration of electrode polarizations. Fig. 2 Energy spectra of the tunnel junction as a function of total magnetic quantum-number m for electron-number n ¼ 0 (solid squares), 1 (solid circles), 2 (solid triangles): (a) This journal is

Spin-polarization inversion of transport current and tunnel magnetoresistance through a non-collinear uniaxial-molecule-magnet dimer junction with electrode magnetization

“…in which r as is state density. Obviously when q ¼ 0 the tunneling strength reduces to that of a collinear molecule-magnet-dimer junction, 33 while in the perpendicular case (q ¼ p/2), the two effective tunneling strengths become equal G a+ ¼ G aÀ similar to the normal metallic electrodes. We consider only the weak coupling of…”

“…It was theoretically and experimentally demonstrated for the rst time that TAMR exists equally well in the AFM leads. 31,32 In a previous paper, 33 we reported spin-polarized transport through a magnetic tunnel junction, in which a molecule-magnet-dimer is embedded. The uniaxial anisotropy axis of a SMM is assumed to be collinear with the electrode polarization.…”

“…In the unit convention ħ ¼ 1 and e ¼ 1, as in the literature, 24,38 we assume that all of the model parameters are the same as those in ref. 33, where the spin of the SMM S ¼ 3/2, anisotropy parameter K ¼ 0.1, inter-SMM Coulomb-repulsionpotential U ¼ 1.5, electron energy levels 3 1 ¼ 0.6 and 3 2 ¼ 0.4, hopping strength t ¼ 0.2, k B T ¼ 0.04, and G ¼ 0.0005 (the units of energy and voltage are meV throughout the paper). The lead polarization parameter in the symmetric condition, eqn (15), is assumed to be p ¼ 0.5.…”

Non-equilibrium quantum transport of spin-polarized electrons and back action on molecular magnet tunnel-junction

“…11,12 The quantum transport through a SMM has been studied extensively, for instance, with spin bias, external magnetic fields and therm power to generate pure spin-polarized current and tunnel magnetoresistance. [13][14][15] The spin polarized current is also investigated with quantum dot, [16][17][18][19][20][21] magnetic semiconductor quantum-well 22,23 and magnetic multilayer-tunnel-junction. [24][25][26][27][28][29] As a back action the SMM can be also manipulated by the spin-polarized current, which affects the magnetization orientation of the SMM via the spin exchange interaction between electron spin and molecule giant-spin.…”