Electronic and Vibrational Properties of Fe2NiAl and Co2NiAl Full Heusler Alloys: A First-Principles Comparison

10.36227/techrxiv.16917469.v1 ◽

2021 ◽

Author(s):

Olga Miroshkina ◽

Vladimir Sokolovskiy ◽

Vasiliy Buchelnikov ◽

Markus Gruner

Keyword(s):

Ground State ◽

First Principles ◽

Low Temperatures ◽

Permanent Magnets ◽

Heusler Alloys ◽

Heusler Compounds ◽

Cubic Lattice ◽

Full Heusler ◽

Full Heusler Alloys ◽

Vibrational Density

In this work, we report on a systematic first-principles study of the structural, electronic, vibrational and thermodynamic properties of the cubic Fe2NiAl and tetragonally distorted Co2NiAl full Heusler compounds. We discuss systematically the competition between the inverse Heusler structure and a Tp-type layered atomic ordering formed by the alternating planes of (Fe,Co) and Ni atoms in terms of the electronic and vibrational density of states. Such an arrangement is predicted to be the ground state of Fe2NiAl. For Co2NiAl, layered ordering has slightly higher energy in comparison with the inverse one, however, we show that it might be stabilized at rather low temperatures. Due to the broken symmetry, layered Tp-Fe2NiAl possesses a large MAE of the same order as tetrataenite FeNi - even in a phase with cubic lattice parameters, which makes a Tp-type layered order an interesting feature for rare-earth free permanent magnets in Heusler-type compounds.

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Competition between cubic and tetragonal phases in all-d-metal Heusler alloys, X 2−x Mn1+x V (X = Pd, Ni, Pt, Ag, Au, Ir, Co; x = 1, 0): a new potential direction of the Heusler family

IUCrJ ◽

10.1107/s2052252519004007 ◽

2019 ◽

Vol 6 (3) ◽

pp. 465-472 ◽

Cited By ~ 15

Author(s):

Yilin Han ◽

Mengxin Wu ◽

Yu Feng ◽

Zhenxiang Cheng ◽

Tingting Lin ◽

...

Keyword(s):

Ground State ◽

First Principles ◽

Heusler Alloys ◽

Cubic Phase ◽

Site Preference ◽

Phonon Spectra ◽

Metal Materials ◽

The Stability ◽

Full Heusler ◽

Full Heusler Alloys

In this work, a series of all-d-metal Heusler alloys, X 2 − x Mn1 + x V (X = Pd, Ni, Pt, Ag, Au, Ir, Co; x; = 1, 0), were predicted by first principles. The series can be roughly divided into two categories: XMn2V (Mn-rich type) and X 2MnV (Mn-poor type). Using optimized structural analysis, it is shown that the ground state of these all-d-metal Heusler alloys does not fully meet the site-preference rule for classic full-Heusler alloys. All the Mn-rich type alloys tend to form the L21 structure, where the two Mn atoms prefer to occupy the A (0, 0, 0) and C (0.5, 0.5, 0.5) Wyckoff sites, whereas for the Mn-poor-type alloys, some are stable with XA structures and some are not. The c/a ratio was also changed while maintaining the volume the same as in the cubic state to investigate the possible tetragonal transformation of these alloys. The Mn-rich Heusler alloys have strong cubic resistance; however, all the Mn-poor alloys prefer to have a tetragonal state instead of a cubic phase through tetragonal transformations. The origin of the tetragonal state and the competition between the cubic and tetragonal phases in Mn-poor alloys are discussed in detail. Results show that broader and shallower density-of-states structures at or in the vicinity of the Fermi level lower the total energy and stabilize the tetragonal phases of X 2MnV (X = Pd, Ni, Pt, Ag, Au, Ir, Co). Furthermore, the lack of virtual frequency in the phonon spectra confirms the stability of the tetragonal states of these Mn-poor all-d-metal Heusler alloys. This work provides relevant experimental guidance in the search for possible martensitic Heusler alloys in all-d-metal materials with less Mn and new spintronic and magnetic intelligent materials among all-d-metal Heusler alloys.

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