Local structure in amorphous Sm$$_x$$Co$$_{1-x}$$: a combined experimental and theoretical study

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 1Àx (x ¼ 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.

Multi-technique Approach to Unravel the (Dis)order in Amorphous Materials

“…Other VP shapes are system-specific: for instance, the (4, 1, 0, 0) has a probability of 0.63% for the Ge 0.4 Se 0.6 while only 0.11 and 0.02% for Ge 0.5 Se 0.5 and Ge 0.4 Se 0.6 , respectively. A similar variability has been already detected in metallic glasses. ,− However, with respect to metallic glasses where common VPs are (0,2,8,2), we detected structures containing abundant n 3 faces but only few n 4 , n 5 , and n 6 faces. This difference suggests that the Ge x Se 1– x compounds are less faceted than typical metallic glasses.…”

“…In order to describe the MRO, we adopted the Voronoi tessellation method, which has been initially employed in the field of metallic glasses. − At odds with the approaches discussed above that are driven by bond orientation, the Voronoi approach relies on purely geometrical assessments, being the decomposition of the metric space with respect to a discrete sample of volumetric elements. Thus, a priori chemical or physical characterization of the sample is not required.…”

Unveiling the local structure of the amorphous metal $$\text {Fe}_{(1-x)}\text {Zr}_x$$ combining first-principles-based simulations and modelling of EXAFS spectra

“…An accurate and valid atomic structure is a prerequisite for meaningful first-principles modelling of other physical properties. Extended X-ray absorption fine structure (EXAFS) data are sensitive to the short-range order and have been used to qualitatively validate simulated amorphous structures for a few amorphous alloys 9 , 17 , 18 . Many details of the atomic structure of amorphous systems are however still unknown.…”

Comparison of the in-plane coercive field and anomalous Nernst effect between a co-sputtered Sm–Co amorphous film and Sm/Co multilayer amorphous films with various layer thicknesses

“…The magnetic anisotropies and interactions that originated from the short-to medium-range ordering of Sm and Co alloys in these amorphous structures depending on microstructural ordering are possible origins of such magnetic nature. 19,20) However, the detailed microscopic origin of this property remains to be investigated. The present magnetic characterization suggests that the t ⩽ 1.0 nm films, including the co-sputtered Sm 20 Co 80 film, behave as an Sm-Co-based alloy/solid-solution with similar microstructural ordering, 15) while the multilayer structure affects the magnetization behavior of the t > 1.0 nm films.…”