Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films.

A Alberca,C Munuera,J Tornos,F J Mompean,N M Nemes,A M Perez-Muñoz,B Kirby,C Leon,J Azpeitia,M Garcia-Hernandez,J Santamaria

doi:10.1038/srep17926

Abstract

We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30–40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2–5)·10−7 s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite.

Highlights

We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates
We investigate the magnetoelectric effect in two different types of BTO substrates characterized by the presence of either only “c”-type FE domains, withpolarization pointing only along the normal to the sample surface, at room temperature, or having both “a”- and “c”-type domains within-plane and out-of-plane polarizations, respectively, present
Two remarkable differences can be observed upon electric field application: i) strong reduction (38%) of the saturation moment, decreasing from Msat ≈ 1.9 μ B/Mn to Msat ≈ 1.1 μ B/Mn and, ii) reduction of the coercive fields, from 450 Oe to 150 Oe

Summary

Introduction

We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30–40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2–5)·10−7 s/m. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/ BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite. The converse magnetoelectric effect (ME)[3] observed in multiferroic materials that exhibit simultaneously ferroelectricity and magnetism opens a way to electrically control magnetization[4,5].

Methods

Results

Conclusion