Characterization of new ferromagnetic Fe-Co-Zn-Ga alloys by ab initio investigations

Abstract

Abstract.We have calculated structural energy differences, magnetic interaction constants and mixing energies of Fe-Co-Ga(Zn) alloys in order to gain information about their suitability for ferromagnetic shape memory devices. We considered the classical Heusler structure as well as an ordering type in which the Co and one Fe sublattice are interchanged. The results of our density functional theory investigations suggest high Curie and martensitic phase transition temperatures for the Ga-based as well as for the Zn-based systems. In case of hypothetical Fe2CoZn alloys, the classically ordered Heusler structure is energetically preferred. In Ga based alloys, the ordering type with Co partially on Fe sites appears to be more stable. We propose that a systematic variation of composition by successive addition of Zn and Co to Fe-Co-Ga may result in a promising new ferromagnetic shape memory alloy of type Fe2−xCo1+xGa1−yZny.

Size-dependent properties of single domain Fe2CoGa nanoparticles prepared by a facile template-less chemical route

“…3 shows that the energy versus volume graph for the X type structure is lower than that of L2 1 , confirming that the stable structure of this alloy is the inverse Heusler (X) structure. Previous total energy calculations performed on this system by Gilleben et al 25 and Dannenberg et al 26,27 agree with our results.…”

“…The lattice parameter of all the samples (see Table 2) obtained from Rietveld refinement was found to be very close to the previously reported values ranging from 5.727 Å to 5.812 Å. 23,[25][26][27]29,33 Table 2 shows the average crystalline size of all the three nanoparticles estimated using Sche ¨rrer's equation. 44 It can be seen that the crystallite size decreases with a decrease in heat treatment temperature or time with hardly any change in the overall composition of the three samples.…”

“…22 Among these Heusler compounds, Fe 2 CoGa occupies a special place due to its high magnetic moment [23][24][25][26][27][28][29][30] and high Curie temperature. 26,27,31,32 Most of the published reports on Fe 2 CoGa alloys are of theoretical/computational [24][25][26][27][28][29][30] nature with a few experimental studies on the bulk form 23,31,33 which provide only a limited amount of information concerning its crystal structure and magnetic nature. There is only one report by Wang et al 18 on the synthesis of Fe 2 CoGa nanoparticles using a silica-assisted chemical method.…”

Spin excitations in Co2NiGa under pressure from a theoretical approach

“…The equilibrium cell parameter has been reported in Table 1, which agrees well with the values previously reported [12]. The bulk modulus has been calculated to be 180.2 GPa, which is in good agreement with previous results [12] and also in close agreement with similar Heusler allows such as Ni 2 MnGa 156 GPa [38], Ni 2 CoGa 194.5 GPa a [39], Fe 2 NiGa 146 GPa [40]. Table 1 also reports the next nearest neighbor distances between different atoms in the optimized unit cell.…”

“…The calculated J have been found to be of the same order of magnitude as reported in the literature for other Heusler structures, e.g. for Fe 2 CoGa, J Fe-Fe 1 = 18 meV and J Fe-Fe 2 = 1 meV [40]. The larger magnitude of the interactions in the Fe-based Heusler system can be attributed to the larger magnetic moment of Fe leading to strong Fe-Fe interactions.…”