Geometric tuning of charge and spin correlations in manganite superlattices

TL;DR

This study demonstrates how varying layer thickness in manganite superlattices can geometrically tune charge and spin correlations, affecting magnetotransport properties and enabling control over electronic regimes.

Contribution

It introduces a method to modulate charge and spin interactions in manganite superlattices through geometric layer tuning, revealing new control over transport phenomena.

Findings

Charge transport is confined to interfaces and occurs via VRH.

Increasing layer thickness suppresses electrostatic screening and opens a Coulomb gap.

At a critical thickness, positive low-field MR emerges due to exchange coupling.

Abstract

We report a modulation of the in-plane magnetotransport in artificial manganite superlattice (SL) [(NdMnO3)n /(SrMnO3)n /(LaMnO3)n]m by varying the layer thickness n while keeping the total thickness of the structure constant. Charge transport in these heterostructures is confined to the interfaces and occurs via variable range hopping (VRH). Upon increasing n, the interfacial separation rises, leading to a suppression of the electrostatic screening between carriers of neighboring interfaces and the opening of a Coulomb gap at the Fermi level (EF). The high-field magnetoresistance (MR) is universally negative due to progressive spin alignment. However at a critical thickness of n=5 unit cells (u.c.), an exchange field coupling between ferromagnetically ordered interfaces results in positive MR at low magnetic field (H). Our results demonstrate the ability to geometrically tune the electrical transport between regimes dominated by either charge or spin correlations.