The local structure around Ge atoms in Ge-doped magnetite thin films

Yoshio Waseda,Kazumasa Sugiyama,Seishi Abe,Kozo Shinoda

doi:10.1515/htmp-2020-0099

Abstract

AbstractDistribution of Ge atoms between tetrahedral and octahedral sites in the spinel-type structure of Fe2.64Ge0.36O4thin films fabricated by radio frequency sputtering with a composite target of magnetite and Ge has been investigated by extended X-ray absorption fine structure analysis. The local structural changes around the Ge atoms in the films induced by annealing at 573 and 873 K are discussed through comparison of the local structure for sintered crystalline Fe2.7Ge0.3O4in which Ge atoms preferentially located at the tetrahedral site of the spinel-type structure. This work provides successful information on the structural change with magnetic property of the thin films as follows: the Ge atoms statistically distributed at the tetrahedral and octahedral sites of the as-synthesized films and preferentially occupied the tetrahedral site by annealing at 873 K corresponding to the increase in magnetization.

Highlights

Magnetite thin films have attracted much attention as devices exhibiting magnetic properties [1,2,3]
We investigate the local structure around the Ge atoms to clarify Ge atom distribution at the A and B sites in the magnetite thin film
The local structures around the Ge atoms for the film samples and the reference Fe2.7Ge0.3O4 bulk sample were characterized by X-ray absorption spectroscopy (XAS)

Summary

Introduction

Magnetite thin films have attracted much attention as devices exhibiting magnetic properties [1,2,3]. One-eighth of the tetrahedral and half of the octahedral interstices of the cubic-close packed oxide anions (32e) are the A and B sites, respectively. The cations at the A and B sites are coordinated by four and six oxide anions, respectively, with different A–O and B–O interatomic distances. In the case of magnetite, Fe2+ cations usually prefer to occupy the octahedral B sites, and the structure is classified as an “inverse” spinel type. The structural differences are useful to determine the distribution of cations to the two sites. We investigate the local structure around the Ge atoms to clarify Ge atom distribution at the A and B sites in the magnetite thin film

Sample preparation

Single crystal X-ray diffraction

Results and discussion

Thin film formation

Summary