Structure and magnetic properties of Fe2NiZ (Z=Al, Ga, Si and Ge) Heusler alloys

Abstract

The Heusler alloys Fe 2 NiZ (Z=Al, Ga, Si and Ge) have been synthesized and investigated focusing on the phase stability and the magnetic properties. The experimental and theoretical results reveal the covalent bonding originated from p-d hybridization takes an important role in these alloys, which dominates the stability of ordered structure but leads to the decline of the band splitting. The electronic structure shows the IV group main group element (Si and Ge) provides stronger covalent effect than that of the III group element (Al and Ga). It has been found that the variations of the physical parameters, lattice constants, critical ordering temperature, magnetic moments and Curie temperature, precisely follow these covalent characters.

Investigation of the structural competing and atomic ordering in Heusler compounds Fe2NiSi and Ni2FeSi under strain condition

“…The lattice constants are determined by minimizing the total energy for each state, and their values are listed in table 1. The results from our calculations are in good agreement with other experimental measurements and theoretical calculations [37,65–68]. In order to further check the structure stability, we computed the total energy difference between the XA structure and the L2 1 structure at ferromagnetic state under different lattice constants, and the results are plotted in figure 2 c , d .…”

“…Moreover, the total energy curves of ferromagnetic states would converge to the non-magnetic ones at small lattice constants and this is due to the abatement of magnetic moment with decreasing lattice, which will be discussed later. The antiferromagnetic state is not considered simply because the experimentally synthesized Fe 2 NiSi compounds show ferromagnetic configuration with large magnetic moment [65].…”

“…The group of Fe-based and Ni-based Heusler compounds are good candidates for this purpose, such as Fe 2 CrGa has different atomic configuration dependent on the preparation methods, and its magnetization can be significantly enhanced by either Fe-Ga or Cr-Ga disorder [60]; Fe 2 MnGa has martensitic transformation induced by magnetic field, and it is accompanied by spontaneous magnetization [62]; Fe 2 CrAl prepared by ball-milling method has partially disordered B2 CD structure, and it shows both higher Curie temperature and magnetic moments [59]; Ni 2 MnGa undergoes a phase transition from cubic structure at high temperature to tetragonal structure at low temperature [63]; Mn 2 NiGa has the stable tetragonal phase compared to the cubic phase, and it is ferromagnetic in both phases with different magnetic moment [64]. In combination of Fe and Ni together, several experimental studies have synthesized Fe 2 NiZ (Z = Al, Ga, Si and Ge) [37,65,66] along with some theoretical investigations on their electronic and magnetic properties under different structures [67,68]. Results show antisite disorder in Fe 2 NiGe and Fe 2 NiGa tends to enhance the stability of cubic structure [69,70], which is contradictory to the minimum total energy configuration in tetragonal phase when being chemically ordered.…”

Phase Stability and Magnetic Properties of Mn3Z (Z = Al, Ga, In, Tl, Ge, Sn, Pb) Heusler Alloys

“…As we know, with the increase of the lattice constant, the distance between atoms increases, which leads to the weakening of covalent hybridization between atoms. The weakened covalent hybridization will result in an increase of atomic magnetic moments in the Heusler alloys [35,36]. When we compress the lattice along the c-axis (c/a < 1), we see that the dependence of the magnetic moment of Mn(A/C) on c/a ratio shows three different tendency ranges with the change of the volume for Mn3Ga alloy, as shown in Figure 4a. (1) When the volume is small (V = 17 nm 3 ), the magnetic moment of Mn(A/C) atom shows a sharp decrease with the increase of c/a.…”

Electronic Structure and Magnetic Exchange Interaction in Fe2NiAs Compound

“…Fe 2 -based Heusler compounds, as a kind of the Heusler materials, have been predicted to be one of promising materials sources. Among them, Fe 2 NiZ alloys attend current widely interest from a theoretical and experimental points of view [4][5][6][7][8]. Fe 2 NiAs compound, as a subset of the Fe 2 Ni-based Heusler compounds, is of particular in semiconductor spintronics devices.…”