Strain-tunable Tunneling Magnetoresistance And Goos H(a|¨)nchen Effect In Graphene

In this paper, the transfer matrix method to study magnetoresistance ratio and theGoos Ha nchendisplacement of the strain graphene.Due to strain and the local magnetic field to inhibitory effect of tunneling, we havedesigned the normal(N)/ferromagnetic(F)/strained(S)/ferromagnetic(F)/normal(N) graphemesquare barrier structures. For the parallel magnetization configuration, the shifts of the K andK’ valleys are neither identical nor opposite, which could be utilized to generate avalley-polarized current, and with the strain increasing, the trend is more obvious. For theantiparallel magnetization configuration, the K and K’ valleys is still valley-degeneracy,valley-polarized current disappear, the transmission can be blocked by the magnetic-electricbarrier provided by strain-induced pseudomagnetic field. These results have been verified inthe conductance. Such transmission discrepancy results in a tremendous magnetoresistanceratio and be tuned by the strain strength and the gate voltage.The strained graphene-based system under consideration the spin structure. Spin up andspin-down electrons in the ferromagnetic region pass into the stress area.It is shown that theexiting positions of K and K’ transmitted beams, together with their distance D, can be tunedby the strain strength and the inclusion of an electrostatic potential. In addition, D can beenhanced by the wave effect near the valley-dependent transmission resonances. Theenhancement is remarkable for graphene F–S–N junctions. Thus the Goos–H nchen effect oftransmitted beams for a ferromagnetic/strained/normal graphene junction can be utilized todesign a valley and spin beam splitter.