Epitaxial multiferroic perovskite oxide thin films for spintronics

Speaker: Dr Daniel Sando
Affiliation: University of Canterbury

Abstract

Perovskite oxides with chemical formula ABO3 are widely studied for their varied properties including ferroelectricity, magnetism, strongly correlated physics, optical effects, and superconductivity. A thriving research direction using such materials is through their integration as epitaxial thin films, allowing many novel and exotic effects to be discovered [1]. In thin films, the substrate imposed mechanical boundary conditions such as strain, crystallographic orientation and symmetry can dramatically influence the functional properties. More specifically, multiferroic oxide thin films offer new perspectives for spintronics, as the coexistence of ferroelectricity and magnetism in these materials provides an additional handle to control the spin order parameter [2].

In this presentation, I will summarize our recent efforts in understanding the structure-property relationships in ferroelectric and multiferroic perovskite oxide thin films. A key material of interest is bismuth ferrite (BiFeO3 – BFO), which harbours both ferroelectricity and G-type antiferromagnetic order at room temperature. As a result, it shows significant promise in future information storage and computation within spintronics architectures. I will show that by exploiting the substrate-imposed strain and crystal orientation (“epitaxy tricks”), as well as finite size effects (through film thickness) [3], we can tune not only the crystal structure, but also the magnetic textures and thus the functional response. Combining numerous experimental techniques – neutron diffraction, Mössbauer spectroscopy, low-energy Raman spectroscopy, scanning probe and transmission electron microscopy, we form a detailed picture of strain- and orientation-dependent physics in these materials [4,5]. I will conclude the talk with perspectives on device opportunities and give examples of functional applications. These results highlight the promise of perovskite oxide thin films for future magnonics and spintronics.

[1]           Sando D 2022 Strain and orientation engineering in ABO3 perovskite oxide thin films Journal of Physics Condensed Matter 34 153001

[2]           Trassin M 2016 Low energy consumption spintronics using multiferroic heterostructures Journal of Physics Condensed Matter 28 033001

[3]           Burns S R, Sando D, Xu B, Dupé B, Russell L, Deng G, Clements R, Paull O H C, Seidel J, Bellaiche L, Valanoor N and Ulrich C 2019 Expansion of the spin cycloid in multiferroic BiFeO3 thin films NPJ Quantum Mater 4 18

[4]           Sando D, Appert F, Xu B, Paull O, Burns S R, Carrétéro C, Dupé B, Garcia V, Gallais Y, Sacuto A, Cazayous M, Dkhil B, Le Breton J-M, Barthélémy A, Bibes M, Bellaiche L, Nagarajan V and Juraszek J 2019 A magnetic phase diagram for nanoscale epitaxial BiFeO3 films Appl Phys Rev 6 041404

[5]           Paull O, Xu C, Cheng X, Zhang Y, Xu B, Kelley K P, de Marco A, Vasudevan R K, Bellaiche L, Nagarajan V and Sando D 2022 Anisotropic epitaxial stabilization of a low-symmetry ferroelectric with enhanced electromechanical response Nat Mater 21 74