Tunnel magnetoresistance in magnetic tunnel junctions with embedded nanoparticles

TL;DR

This paper presents a theoretical model explaining abnormal tunnel magnetoresistance effects in magnetic tunnel junctions with embedded nanoparticles, highlighting quantum well states and coherent tunneling as key factors.

Contribution

It introduces a quantum well-based tunneling model to explain TMR anomalies in magnetic tunnel junctions with embedded nanoparticles, including sign reversal and suppression effects.

Findings

TMR suppression linked to quantized angle transparency.

Sign reversal of TMR at small voltages explained by quantum well states.

Coherent double barrier tunneling dominates over single barrier tunneling.

Abstract

In this paper, we attempt the theoretical modeling of the magnetic tunnel junctions with embedded magnetic and nonmagnetic nanoparticles (NPs). A few abnormal tunnel magnetoresistance (TMR) effects, observed in related experiments, can be easily simulated within our model: we found, that the suppressed TMR magnitudes and the TMR sign-reversing effect at small voltages are related to the electron momentum states of the NP located inside the insulating layer. All these TMR behaviors can be explained within the tunneling model, where NP is simulated as a quantum well (QW). The coherent (direct) double barrier tunneling is dominating over the single barrier one. The origin of the TMR suppression is the quantized angle transparency for spin polarized electrons being in one of the lowest QW states. The phenomenon was classified as the quantized conductance regime due to restricted geometry.