First-principles calculations and experimental studies on Co2FeGe Heusler alloy nanoparticles for spintronics applications

Highlights: • Here, we report the synthesis and physical properties of Co₂FeGe (CFG) Heusler alloy (HA) nanoparticles (NPs). • The NPs of mean size 23 nm with a dispersion of±10 nm are prepared via the co-precipitation method. • NPs are soft ferromagnetic and exhibit high saturation magnetization (Ms), and a very high Curie temperature (Tc) of 1060 K. • The first-principles density functional theory computations complement the experimental results. • The near-integral value 5.9 μ_B/f.u. of Ms at 5 K indicates that half-metallic ferromagnetism is preserved in these NPs. -- Abstract: Here, we report the synthesis and physical properties of Co₂FeGe (CFG) Heusler alloy (HA) nanoparticles (NPs). The NPs of size 23±10 nm are prepared using the co-precipitation method. X-ray and selected area electron diffraction patterns have confirmed the cubic Heusler phase of the NPs with the A2-disorder. These NPs are soft ferromagnetic, and exhibit a high saturation magnetization (M_s) along with a very high Curie temperature (T_c) of 1060 K. The observed T_c value matches closely with the theoretically calculated one following a model provided by Wurmehl et al. (2005). The high M_s and T_c make the present system a potential candidate for magnetically activated nano-devices working at high temperatures. The near-integral value 5.9 μ_B/f.u. of M_s at low temperatures indicates that the half-metallic ferromagnetism is preserved even in the particles even on the 20 nm length scale. Additionally, we have facilitated the existing HA-NP preparation method, which can be used in synthesizing other HA-NPs. The first-principles density functional theory computations complement the experimental results.