Al substitution effects on phase stabilities and magnetic properties of tetragonal Mn3Ge

Hironari Okada,Yudai Shoji

doi:10.1063/1.5079907

Abstract

We have investigated Al substitution effects on phase stabilities and magnetic properties of Mn3Ge with tetragonal D022 structure. The lattice constant a is expanded, and the c is contracted by substituting Al for Ge. Consequently, the unit cell volume slightly increases with the increasing Al content, although Al atom has smaller ionic radius than Ge atom. These composition dependencies of the structural parameters are influenced by the number of the valence electrons rather than the ionic radius. Thermal stability of the D022 structure is enhanced by the Al substitution. The magnetic curves of the Al-substituted system mostly unchanged, suggesting that the structural properties such as the unit cell volume and the atomic distance between the Mn atoms play an important role for the magnetic properties of the alloy.

Highlights

IntroductionMn3Ga and Mn3Ge alloys with tetragonal D022 structure (space group I4/mmm, TiAl3-type) which is related to Heusler L21 structure have attracted much attention because these alloys exhibit strong uniaxial magnetocrystalline anisotropy without 4f elements and are expected to be candidates for novel spintronic and permanent magnet materials. The D022 structure has crystallographically different two Mn sites, MnI and MnII (Wyckoff positions 2b and 4d, respectively)
Mn3Ga and Mn3Ge alloys with tetragonal D022 structure which is related to Heusler L21 structure have attracted much attention because these alloys exhibit strong uniaxial magnetocrystalline anisotropy without 4f elements and are expected to be candidates for novel spintronic and permanent magnet materials.1–4 The D022 structure has crystallographically different two Mn sites, MnI and MnII (Wyckoff positions 2b and 4d, respectively)
All the samples synthesized in this paper are mostly composed of the D022 phase, but an impurity phase with the β-Mn structure is stabilized by introducing Al and excess Mn

Summary

Introduction

Mn3Ga and Mn3Ge alloys with tetragonal D022 structure (space group I4/mmm, TiAl3-type) which is related to Heusler L21 structure have attracted much attention because these alloys exhibit strong uniaxial magnetocrystalline anisotropy without 4f elements and are expected to be candidates for novel spintronic and permanent magnet materials. The D022 structure has crystallographically different two Mn sites, MnI and MnII (Wyckoff positions 2b and 4d, respectively). Mn3Ga and Mn3Ge alloys with tetragonal D022 structure (space group I4/mmm, TiAl3-type) which is related to Heusler L21 structure have attracted much attention because these alloys exhibit strong uniaxial magnetocrystalline anisotropy without 4f elements and are expected to be candidates for novel spintronic and permanent magnet materials.. The D022 structure has crystallographically different two Mn sites, MnI and MnII (Wyckoff positions 2b and 4d, respectively). The magnetic moments of the MnI and MnII sites are antiferromagnetically coupled, resulting in a ferrimagnetic ordering of the alloys.. It has been reported that the magnetic properties of the Mnbased alloys are strongly influenced by the number of the valence electron.. The theoretical investigation predicted that the exchange interaction between the two Mn sites is sensitive to structural properties such as an atomic ordering, an off-stoichiometry and an atomic distance. It has been reported that the magnetic properties of the Mnbased alloys are strongly influenced by the number of the valence electron. On the other hand, the theoretical investigation predicted that the exchange interaction between the two Mn sites is sensitive to structural properties such as an atomic ordering, an off-stoichiometry and an atomic distance.

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Results

Conclusion