Co2FeAl (CFA) nanoparticles (NPs) of different sizes were synthesized by chemical route. The effect of the size of NPs upon the structure and magnetization compared to its bulk counterpart was investigated. The structure and composition were determined from X-ray diffraction (XRD) and electron microscopy. XRD analysis shows that the samples are having single (A2-type) disordered phase. Magnetization measurements suggest that the samples are soft ferromagnetic in nature with very low coercivity. Enhanced magnetic properties like saturation magnetization, coercive force, retentivity, and Curie-temperature are observed with a decrease in particle size. The effect of particle size on hysteresis losses is also discussed. The smallest particles of size 16 nm exhibited the highest saturation magnetization and transition temperature of 180.73 emu/g and 1261 K, respectively. The origin of enhancement in magnetization of Co2FeAl nano-alloy is attributed to the strong Co-Co exchange interaction due to disorder present in the systems.

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The physical properties of Fe2CoAl (FCA) Heusler alloy have been determined by means of first-principles calculations. We focus on the influence of atomic ordering, with respect to the Wyckoff sites A (0, 0, 0), B (0.25, 0.25, 0.25), C (0.5, 0.5, 0.5) and D (0.75, 0.75, 0.75), on the structural, magnetic and electronic properties in both the conventional L21 (Cu2MnAl prototype) and XA (Hg2CuTi prototype) inverse Heusler structures. Various non-magnetic and magnetic configurations are considered. Out of these, the ferromagnetic XA-I structure is found to be energetically most stable. The total magnetic moments per cell were not in agreement with the Slater-Pauling rule in any phases. Half-metallicity is not observed in any configuration. However, all the structures exhibit high magnetic moment, Curie temperature and spin polarization. The calculated values of total magnetic moment and Curie temperature (Tc) are in a close agreement with the available experimental data. The possibility of making the alloy a half metal is also discussed.

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