Large Magnetoresistance in a Manganite Spin-Tunnel-Junction Using LaMnO3 as Insulating Barrier

TL;DR

This paper theoretically investigates a manganite-based spin-tunnel-junction with LaMnO3 barriers, revealing a highly resistive state with large magnetoresistance that can be controlled by small magnetic fields, influenced by temperature and layer parity.

Contribution

It introduces a theoretical model for manganite spin-tunnel-junctions with LaMnO3 barriers, highlighting the magnetic and transport properties depending on layer number and external fields.

Findings

Even-layer LMO barriers lead to anti-parallel magnetic moments and high resistance.

Small magnetic fields can switch the magnetic state, causing large magnetoresistance.

Temperature and layer parity significantly affect the junction's magnetic and transport behavior.

Abstract

A spin-tunnel-junction based on manganites, with La$_{1-x}$Sr$_x$MnO$_3$ (LSMO) as ferromagnetic metallic electrodes and the undoped parent compound LaMnO$_3$ (LMO) as insulating barrier, is here theoretically discussed using double exchange model Hamiltonians and numerical techniques. For an even number of LMO layers, the ground state is shown to have anti-parallel LSMO magnetic moments. This highly resistive, but fragile, state is easily destabilized by small magnetic fields, which orient the LSMO moments in the direction of the field. The magnetoresistance associated with this transition is very large, according to Monte Carlo and Density Matrix Renormalization Group studies. The influence of temperature, the case of an odd number of LMO layers, and the differences between LMO and SrTiO$_3$ as barriers are also addressed. General trends are discussed.