Local structure in amorphous Sm_xCo_{1-x}: a combined experimental and theoretical study

Sebastian George,Giuseppe Muscas,Gabriella Andersson,Olle Eriksson,Krisztina Kádas,Petra E Jönsson,Fridrik Magnus,Anna Delin

doi:10.1007/s10853-020-04848-4

Abstract

Using a combination of extended X-ray absorption fine structure measurements, stochastic quenching (SQ) calculations and Voronoi tessellation analysis, the local atomic environments in thin films of amorphous Sm_{x}Co_{1-x} (x = 0.10, 0.22 and 0.35) are investigated and also compared with crystalline stoichiometric Sm–Co alloys of similar compositions. It is found that the variations in local environment around Co atoms in the amorphous films increase with increasing x and that none of the films exhibit any pronounced short-range order around the Sm atoms. There are, however, signs of clustering of Sm atoms in the SQ-generated simulated amorphous materials.Furthermore, good agreement is observed between experimentally obtained parameters, e.g., interatomic distances and coordination numbers, and those extracted from the simulated alloys. This is a strong indication that SQ provides a powerful route to reliable local structure information for amorphous rare earth–transition metal alloys and that it could be used for designing materials with properties that meet the demands of specific applications.

Highlights

Amorphous magnetic materials continue to be of fundamental and technological interest due to a number of appealing properties
This is a strong indication that stochastic quenching (SQ) provides a powerful route to reliable local structure information for amorphous rare earth–transition metal alloys and that it could be used for designing materials with properties that meet the demands of specific applications
Actual compositions were determined via Rutherford backscattering spectrometry (RBS) at the Tandem Laboratory, Uppsala, and the thickness and density of each film were determined by X-ray reflectivity (XRR)

Summary

Introduction

Amorphous magnetic materials continue to be of fundamental and technological interest due to a number of appealing properties They typically have low coercivities and reduced electrical conductivity when compared to their crystalline counterparts, opening up a wide variety of potential applications both in bulk [1] and thin film form [2,3,4], especially since properties can be changed within wide ranges by altering the composition. While the magnetic properties are relatively straightforward to characterize experimentally, developing a detailed theoretical understanding of their origin is quite challenging. This is due in large part to a limited knowledge of the local atomic structure. Throughout this paper, we will use the term ‘structure’ in a rather broad sense, to incorporate arrangements of atoms in amorphous materials

Methods

Results

Conclusion