New quaternary half-metallic ferromagnets with large Curie temperatures

Ashis Kundu,Subhradip Ghosh,Srikrishna Ghosh,Rudra Banerjee,Biplab Sanyal

doi:10.1038/s41598-017-01782-5

Ashis Kundu, Subhradip Ghosh + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-01782-5

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Abstract

New magnetic materials with high Curie temperatures for spintronic applications are perpetually sought for. In this paper, we present an ab initio study of the structural, electronic and magnetic properties of Quaternary Heusler compounds CoX′Y′Si where X′ is a transition metal with 4d electrons and Y′ is either Fe or Mn. We find five new half-metallic ferromagnets with spin polarisation nearly 100% with very high Curie temperatures. The variation of Curie temperatures as a function of valence electrons can be understood from the calculated inter-atomic exchange interaction parameters. We also identify a few other compounds, which could be potential half-metals with suitable application of pressure or with controlled doping. Our results reveal that the half-metallicity in these compounds is intricately related to the arrangements of the magnetic atoms in the Heusler lattice and hence, the interatomic exchange interactions between the moments. The trends in the atomic arrangements, total and local magnetic moments, interatomic magnetic exchange interactions and Curie temperatures are discussed with fundamental insights.

Highlights

The study of intermetallic Heusler compounds has gained significant momentum over the last decade due to their exceptional qualities in displaying wide varieties of properties, ranging from half-metallic magnetism, magnetic shape memory effect, spin gapless semiconductor to giant magnetocaloric effect, thermoelectric effect and superconductivity[1,2,3,4,5,6]
We have made a detailed investigations into the structural, electronic and magnetic properties of 18 Quaternary Heusler compounds spanning the series CoX′Y′Si, where X′ stand for 9 elements with 4d electrons in their valence shells, and Y′ being Fe and Mn, the two strong magnets with unfilled 3d electrons in their outer shells
It has been found that three compounds CoTcMnSi, CoRhMnSi and CoZrFeSi can be identified as truly half-metals

Summary

Introduction

The study of intermetallic Heusler compounds has gained significant momentum over the last decade due to their exceptional qualities in displaying wide varieties of properties, ranging from half-metallic magnetism, magnetic shape memory effect, spin gapless semiconductor to giant magnetocaloric effect, thermoelectric effect and superconductivity[1,2,3,4,5,6]. Apart from the quest for new materials, our motivations were (1) to understand the effects of the presence of an element with 4d electrons on the structure, electronic and magnetic properties of compounds where the other two magnetic elements are from 3d transition metal series and (2) To understand the role of the 4d transition metal elements by successively changing it along the series of 4d transition metals so that the total electron number changes continuously, on the properties of compounds where one of the 3d elements remains fixed while the other changes To this end, we have used Density functional theory (DFT) based electronic structure method to compute the electronic structures, the structural, electronic and magnetic properties of quaternary CoX′MnSi and CoX′FeSi compounds where X′ varies from Y to Ag. We have explored the ground state sub-lattice occupancies and the magnetic structures of each compound. The methods used in this work are given at the end

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Conclusion