Experimental and first-principles determination of the magnetocrystalline anisotropy in MnxGa

Xubo Liu,D H Ryan,Ming Yue,Hongguo Zhang,Manli Wang,Qingmei Lu,Z Altounian

doi:10.1063/1.4974890

Xubo Liu, D H Ryan + Show 5 more

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https://doi.org/10.1063/1.4974890

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Journal: AIP Advances	Publication Date: Jan 20, 2017
Citations: 6	License type: CC BY 4.0

Affiliation: McGill University, Beijing University of Technology

Abstract

Singular point detection (SPD) for the determination of the anisotropy field (BA) using a conventional magnetometer is demonstrated. We then follow the composition dependence of BA in MnxGa using a combination of SPD measurements complemented by first-principles density functional theory (DFT) calculations. We find excellent quantitative agreement for 1.2≤x≤ 1.8, but observe a marked departure for x≤1.2. We suggest that the deviation from ideal behaviour might be associated with site disorder at low excess Mn.

Highlights

Manganese-based magnetic compounds are being investigated for two main reasons: (1) they avoid the need for rare earths, (2) they offer a modest-cost/modest performance alternative to the two dominant hard magnet technologies based on Nd2Fe14B (515 kJ m3) and Ba(Sr)Fe12O19.One possible such system is Mn-Ga
In our previous work on the MnxGa hard magnet system we concentrated on the crystal structure and basic magnetic properties (Tc and saturation magnetisation).[1,2,3]
We demonstrate that a conventional extraction magnetometer (Quantum Design Physical Properties Measurement System – PPMS) can be used to determine the anisotropy field (BA) using the singular point detection method

Summary

Introduction

Manganese-based magnetic compounds are being investigated for two main reasons: (1) they avoid the need for rare earths, (2) they offer a modest-cost/modest performance alternative to the two dominant hard magnet technologies based on Nd2Fe14B (515 kJ m3) and Ba(Sr)Fe12O19. One possible such system is Mn-Ga. the Mn-Ga binary phase diagram is extremely complex, lacking a single congruently-melting compound. In order to assess the possible applications of MnxGa as a new, rare-earth free hard magnetic material it is essential to start by establishing the intrinsic properties of well characterised single-phased materials as these parameters set the limits on what might be achieved through appropriate optimisation through doping and heat treatments. In our previous work on the MnxGa hard magnet system we concentrated on the crystal structure and basic magnetic properties (Tc and saturation magnetisation).[1,2,3] We showed that the system adopts a primitive tetragonal structure (P4/mmm #123, sometimes denoted “L10”) with Mn on the

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