Extraordinary Hall resistance and unconventional magnetoresistance in Pt/LaCoO3 hybrids

TL;DR

This study investigates unusual Hall resistance and magnetoresistance in Pt films on LaCoO3, revealing significant effects linked to ferromagnetic transitions, which challenge existing theories and suggest new mechanisms.

Contribution

It reports novel extraordinary Hall resistance and unconventional magnetoresistance in Pt/LaCoO3 hybrids, highlighting phenomena not explained by current theories.

Findings

Significant extraordinary Hall resistance up to 50 mΩ observed.

Unconventional magnetoresistance ratio around 1.2×10^{-4}.

Features differ from Y3Fe5O12-based Pt films.

Abstract

We report an investigation of transverse Hall resistance and longitudinal resistance on Pt thin films sputtered on epitaxial LaCoO$_3$ (LCO) ferromagnetic insulator films. The LaCoO$_3$ films were deposited on several single crystalline substrates [LaAlO$_3$ (LAO), (La,Sr)(Al,Ta)O$_3$ (LSAT), and SrTiO$_3$ (STO)] with (001) orientation. The physical properties of LaCoO$_3$ films were characterized by the measurements of magnetic and transport properties. The LaCoO$_3$ films undergo a paramagnetic to ferromagnetic (FM) transition at Curie temperatures ranging from 40 K to 85 K, below which the Pt/LCO hybrids exhibit significant extraordinary Hall resistance (EHR) up to 50 m$\Omega$ and unconventional magnetoresistance (UCMR) ratio $\Delta$$\rho$/$\rho_0$ about $1.2 \times 10^{-4}$, accompanied by the conventional magnetoresistance (CMR). The observed spin transport properties share some common features as well as some unique characteristics when compared with well-studied Y$_3$Fe$_5$O$_{12}$-based Pt thin films. Our findings call for new theories since the extraordinary Hall resistance and magnetoresistance cannot be consistently explained by the existing theories.