Magnetic anisotropy in strained manganite films and bicrystal junctions

TL;DR

This study investigates the magnetic anisotropy and magnetoresistance in strained LSMO manganite films and bicrystal junctions, revealing how substrate type, inclination, and boundary misorientation influence magnetic properties and electron scattering mechanisms.

Contribution

It provides new insights into how substrate-induced strain and bicrystal boundary configurations affect magnetic anisotropy and magnetoresistance in manganite thin films.

Findings

Orthorhombic NGO substrates induce uniaxial anisotropy.

Magnetic anisotropy varies with substrate inclination angle.

Magnetoresistance increases with temperature and misorientation angle.

Abstract

Transport and magnetic properties of LSMO manganite thin films and bicrystal junctions were investigated. Manganite films were epitaxially grown on STO, LAO, NGO and LSAT substrates and their magnetic anisotropy were determined by two techniques of magnetic resonance spectroscopy. Compare with cubic substrates a small (about 0.3 persentage), the anisotropy of the orthorhombic NGO substrate leads to a uniaxial anisotropy of the magnetic properties of the films in the plane of the substrate. Samples with different tilt of crystallographic basal planes of manganite as well as bicrystal junctions with rotation of the crystallographic axes (RB - junction) and with tilting of basal planes (TB - junction) were investigated. It was found that on vicinal NGO substrates the value of magnetic anisotropy could be varied by changing the substrate inclination angle from 0 to 25 degrees. Measurement of magnetic anisotropy of manganite bicrystal junction demonstrated the presence of two ferromagnetically ordered spin subsystems for both types of bicrystal boundaries RB and TB. The magnitude of the magnetoresistance for TB - junctions increased with decreasing temperature and with the misorientation angle even misorientation of easy axes in the parts of junction does not change. Analysis of the voltage dependencies of bicrystal junction conductivity show that the low value of the magnetoresistance for the LSMO bicrystal junctions can be caused by two scattering mechanisms with the spin- flip of spin - polarized carriers due to the strong electron - electron interactions in a disordered layer at the bicrystal boundary at low temperatures and the spin-flip by anti ferromagnetic magnons at high temperatures.