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

TL;DR

This paper introduces the 'Brillouin zone spin filtering' mechanism in Co/h-BN/Co magnetic tunnel junctions, predicting high TMR sensitive to Fermi level shifts, and highlights the importance of correlation effects for accurate modeling, suggesting potential for STT-MRAM applications.

Contribution

The study demonstrates a new spin filtering mechanism in Co/h-BN/Co MTJs and emphasizes the role of correlation effects for accurate transport property predictions.

Findings

High TMR predicted due to Brillouin zone filtering.

TMR varies significantly with Fermi energy shifts.

Correlation effects are essential for accurate Fermi level positioning.

Abstract

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