Single-crystal high entropy perovskite oxide epitaxial films

Yogesh Sharma,Xiang Gao,Andreas Herklotz,Ankur Rastogi,Ho Nyung Lee,Andrew F May,Brianna L Musico,T Zac Ward,Chengyun Hua,Jiaqiang Yan,Matthew F Chisholm,David Mandrus,Veerle Keppens

doi:10.1103/physrevmaterials.2.060404

Abstract

The first examples of single crystal epitaxial thin films of a high entropy perovskite oxide are synthesized. Pulsed laser deposition is used to grow the configurationally disordered ABO3 perovskite, Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3, epitaxially on SrTiO3 and MgO substrates. X-ray diffraction and scanning transmission electron microscopy demonstrate that the films are single phase with excellent crystallinity and atomically abrupt interfaces to the underlying substrates. Atomically-resolved electron energy loss spectroscopy mapping shows a uniform and random distribution of all B-site cations. The ability to stabilize perovskites with this level of configurational disorder offers new possibilities for designing materials from a much broader combinatorial cation pallet while providing a fresh avenue for fundamental studies in strongly correlated quantum materials where local disorder can play a critical role in determining macroscopic properties.

Highlights

The ABO3 perovskite oxide structure and its derivatives are of broad interest to the study and application of magnetism [1], energy conversion and storage [2,3], superconductivity [4], topology [5], ferroics [6,7,8], and a host of other phenomena
This substitutional approach is a central pillar of materials design strategies—with the search for new functionally relevant materials often beginning with a parent ABO3 ternary compound which is partially substitutionally doped to an [AxA1-x]BO3 or A[BxB1-x]O3 quaternary compound of superior character or novel physical behavior [9,10]
Film uniformity is excellent as demonstrated by Laue oscillations on the high entropy perovskite oxide (HEPO) film 002 peak in Fig. 1(b) and the x-ray reflectivity (XRR) measurements where the periodic oscillations arising from the interfacial interference can be observed and fit to give thicknesses of 7, 26, and 72 nm

Summary

INTRODUCTION

The ABO3 perovskite oxide structure and its derivatives are of broad interest to the study and application of magnetism [1], energy conversion and storage [2,3], superconductivity [4], topology [5], ferroics [6,7,8], and a host of other phenomena. The rocksalt structure was stabilized in epitaxial thin-film form and, driven by the inherent local disorder of the HEO, shown to induce an order of magnitude increase in exchange coupling response at a ferromagnetic nickel-iron alloy interface. If such large disorder-mediated responses can be utilized in this relatively simple structure, the perovskite structure may offer even greater novelty of response due to its often extreme sensitivity to disorder. Since the B-site sublattice is most often responsible for ferroic, magnetic, and electronic transport properties, the capability to select designer combinations of B-site stoichiometries offers new options to tailoring materials’ properties and will likely lead to previously unobserved disorder-driven physical responses

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSIONS