Interrelation among superstructural ordering, oxygen nonstoichiometry and lattice strain of double perovskite Sr2FeMoO6−δ materials

Nikolay Kalanda,Chanyong Hwang,Lin Huang,Ivan Bobrikov,Victor Kuts,Dmitry Karpinsky,Marta Yarmolich,Dong-Hyun Kim

doi:10.1007/s10853-021-06072-0

Abstract

Double perovskite ceramics Sr2FeMoO6−δ having different amount of antisite disordering and oxygen content are prepared by the solid-phase reaction method using SrFeO2.52(3) and SrMoO4 initial reagents. X-ray and neutron diffraction techniques are used to estimate a modification in the structural parameters as a function of oxygen content and B-site cationic ordering. The reduction in the oxygen content leads to an increase in the unit cell volume, which is mainly associated with an elongation of c-parameter of the tetragonal unit cell and relative expansion of the chemical bonds between Mo/Fe ions and apical oxygen ions. Superstructural ordering observed for the compounds causes a decrease in the unit cell volume, which is accompanied by a reduction in the length of the Mo/Fe–O bonds, located in the basal plane of oxygen octahedra. This modification of the unit cell parameters notably affects a character of the exchange interactions formed between B-site ions thus allowing to control magnetic and transport properties of Sr2FeMoO6−δ ceramics. It is found that comprehensive approach allows a consistent understanding of much debated structural/magnetic behaviors of double perovskite Sr2FeMoO6−δ systems, opening a venue for designing reliable devices based on the half-metallic double perovskite materials.

Highlights

Strontium ferromolybdate Sr2FeMoO6-d (SFMO) with double perovskite structure is a prospective material for various applications in modern electronic industry, such as nonvolatile magnetoresistive random-access memory (MRAM), magnetic read/ write heads for hard disk drives, highly sensitive magnetic field sensors and electrodes for solid fuel cells [1–4]
Physicochemical properties of the SFMO considerably depend on the oxygen stoichiometry, which influences the degree of superstructural ordering of iron and molybdenum cations, the orbital, charge and spin degrees of freedom, and these properties depend on the electronic exchange interaction between Fe3? and Mo5?
Analysis of the saturation rates of the oxygen index and the degree of cations ordering of Sr2FeMoO5.99(1) samples was performed based on the isothermal dependencies having the form: (6 - d) = f1(t) and P = f2(t)

Summary

Introduction

Strontium ferromolybdate Sr2FeMoO6-d (SFMO) with double perovskite structure is a prospective material for various applications in modern electronic industry, such as nonvolatile magnetoresistive random-access memory (MRAM), magnetic read/ write heads for hard disk drives, highly sensitive magnetic field sensors and electrodes for solid fuel cells [1–4]. These applications require the use of structurally perfect SFMO samples with Curie point above room temperature (TC), high saturation magnetization (Ms), large degree of Fe/Mo cations superstructural ordering (P) as well as high spin polarization of free (delocalized) electrons [5–8]. Any distortions of the crystal lattice caused by oxygen deficiency have a strong effect on the electrical transport and magnetic properties of strontium ferromolybdate [9, 10]

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