Structural Characterization and Physical Properties of Double Perovskite La2FeReO6+δ Powders.

Qingkai Tang,Xinhua Zhu

doi:10.3390/nano12020244

Abstract

The structural, optical, dielectric, and magnetic properties of double perovskite La2FeReO6+δ (LFRO) powders synthesized by solid-state reaction method under CO reduced atmosphere are reported on in this paper. Reitveld refinements on the XRD data revealed that the LFRO powders crystallized in an orthogonal structure (Pbnm space group) with column-like morphology. The molar ratios of La, Fe, and Re elements were close to 2:1:1. XPS spectra verified the mixed chemical states of Fe and Re ions, and two oxygen species in the LFRO powders. The LFRO ceramics exhibited a relaxor-like dielectric behavior, and the associated activation energy was 0.05 eV. Possible origins of the dielectric relaxation behavior are discussed based on the hopping of electrons among the hetero-valence ions at B-site, oxygen ion hopping through the vacant oxygen sites, and the jumping of electrons trapped in the shallower level created by oxygen vacancy. The LFRO powders display room temperature ferromagnetism with Curie temperature of 746 K. A Griffiths-like phase was observed in the LFRO powders with a Griffiths temperature of 758 K. The direct optical band gap of the LFRO powders was 2.30 eV, deduced from their absorption spectra, as confirmed by their green photoluminescence spectra with a strong peak around 556 nm.

Highlights

With the development of modern microelectronics, transistor manufacturing technology based on electronic charge transportation faces great challenges—such as the continuous reduction in the feature size and the size effect, increased leakage current, and so on—which stimulate the development of spintronics and spintronic devices that are based on the electron spin and the spin half-metallic (HM) materials [1,2]
Structural, dielectric, magnetic, and optical properties of the La2 FeReO6+δ powders synthesized by solid-state reaction under reducing atmosphere of CO, are investigated
SEM images demonstrated that the LFRO powders exhibited column-like morphology with slight agglomeration and the particle sizes were in the range of 40–450 nm

Summary

Introduction

With the development of modern microelectronics, transistor manufacturing technology based on electronic charge transportation faces great challenges—such as the continuous reduction in the feature size and the size effect, increased leakage current, and so on—which stimulate the development of spintronics and spintronic devices that are based on the electron spin and the spin half-metallic (HM) materials ( called HM materials) [1,2]. HM materials are defined as the materials in which only one-spin direction is present at the Fermi level. The density of states of HM materials is fully spin-polarized at the Fermi level. The concept of HM was first proposed in 1983 by de Groot et al during their theoretical calculations of the band structures of magnetic semi-Heusler compounds [6]. Several candidates have been discovered to exhibit HM properties, which include (i) semi-Heusler [6] and full-Heusler alloys [10]; (ii) rutile structured oxides such as CrO2 [11]; (iii) spinel structured compounds such as magnetite Fe3 O4 [12]; (iv) perovskite structured oxides such as La0.7 Sr0.3 MnO3 [13];

Methods

Results

Conclusion