Anomalous Tunnel Magnetoresistance and Spin Transfer Torque in Magnetic Tunnel Junctions with Embedded Nanoparticles.

Arthur Useinov,Niazbeck Useinov,Te-Ho Wu,Lin-Xiu Ye,Chih-Huang Lai

doi:10.1038/srep18026

Abstract

The tunnel magnetoresistance (TMR) in the magnetic tunnel junction (MTJ) with embedded nanoparticles (NPs) was calculated in range of the quantum-ballistic model. The simulation was performed for electron tunneling through the insulating layer with embedded magnetic and non-magnetic NPs within the approach of the double barrier subsystem connected in parallel to the single barrier one. This model can be applied for both MTJs with in-plane magnetization and perpendicular one. We also calculated the in-plane component of the spin transfer torque (STT) versus the applied voltage in MTJs with magnetic NPs and determined that its value can be much larger than in single barrier system (SBS) for the same tunneling thickness. The reported simulation reproduces experimental data of the TMR suppression and peak-like TMR anomalies at low voltages available in leterature.

Highlights

In the present study, the transport problem was explored in terms of electron propagating waves reflecting the superposition of the quantum states for all magnetic layers, barriers and NPs within the double barrier approach[16] and generalized point-like contact model
Recent experimental and theoretical studies confirmed that double barrier magnetic tunnel junctions are promising structures for nanodevices[5,17,18,19,20,21], for instance Gao et al.[19] proposed the fabrication of a new kind of the spintronic devices such as the memory cell or spin transfer torque (STT)-MRAM on the basis of the tunnel junctions, where the insulating layer is deposited as discontinuous media with embedded NPs
In this work demonstrated theoretical technique allows us reproduce tunnel magnetoresistance (TMR) anomalies according to the experimental studies available in literature

Summary

Introduction

The transport problem was explored in terms of electron propagating waves reflecting the superposition of the quantum states for all magnetic layers, barriers and NPs within the double barrier approach[16] and generalized point-like contact model (see Supplementary Information). Up to the present time there is an absence of systematically sufficient theoretical studies in the related field that explain the anomalous TMR behavior appropriately in the system with embedded NPs. The goal of this work is to present a simple approach explaining mainly all kinds of experimental observations, those published by researchers from the IBM Almaden Research Center[11] and Taiwan SPIN Research Center[22]. In comparison with the reference sample without Fe nanoparticles, one order enhancement of TMR value was discovered in the system with small tNP = 0.15 nm This behavior may originate from the possible enhancement of the spin polarization or spin current filtering on NP25, but not due to Coulomb blockade effects

Objectives

Results

Conclusion