Brillouin zone spin filtering mechanism of enhanced TMR and correlation effects in Co(0001)/h-BN/Co(0001) magnetic tunnel junction

摘要

The 'Brillouin zone spin filtering' mechanism of enhanced tunnelingmagnetoresistance (TMR) is described for magnetic tunnel junctions (MTJ) andstudied on an example of the MTJ with hcp Co electrodes and hexagonal BN (h-BN)spacer. Our calculations based on local density approximation of densityfunctional theory (LDA-DFT) for Co(0001)/h-BN/Co(0001) MTJ predict high TMR inthis device due to Brillouin zone filtering mechanism. Owning to the specificcomplex band structure of the h-BN the spin-dependent tunneling conductance ofthe system is ultra-sensitive to small variations of the Fermi energy positioninside the BN band gap. Doping of the BN and, consequentially, changing theFermi energy position could lead to variation of the TMR by several orders ofmagnitude. We show also that taking into account correlation effects on beyondDFT level is required to accurately describe position of the Fermi level andthus transport propertied of the system. Our study suggests that new MTJ basedon hcp Co-Pt or Co-Pd disordered alloy electrodes and p-doped hexagonal BNspacer is a promising candidate for the spin-transfer torque magnetoresistiverandom-access memory (STT-MRAM).