Structure,Magnetic And Transport Properties Of Fe_3-xMn?Co?_xSi Epitaxial Films

Heusler alloys have many advantages such as excellent ferromagnetic properties, good thermal stability, high spin polarization and high Curie temperature. Thus they have become the candidate materials for spintronic devices and the research focus in the field of materials science. Considering that their magnetic properties and spin transport properties strongly depend on the chemical composition and the structure ordering degree, the element substitutions can contribute to deeper understanding of their electronic transport properties, and even to the design of suitable materials for the applications. For the typical binary Heusler alloy Fe3 Si, Mn and Co atoms will respectively replace its internal Fe atoms with different site occupations, resulting in the different crystal structures, magnetic and transport properties.Fe3–xMn(Co)xSi epitaxial films were grown on Mg O substrates by magnetron co-sputtering. The epitaxial relationship is 3Fe Mn(Co) Si(001)[110]||Mg O(001)[100]-x x, and the microstructure, magnetic and transport properties were investigated systematically.It was found that the Fe3-xMnxSi epitaxial films exhibit soft magnetic properties. The saturation magnetization decreases with the increasing Mn content while the coercivity increases. The ZFC–FC curve bifurcates at low temperatures and the bifurcation temperature increases monotonically with the increasing Mn content. This is mainly due to the substitution of Mn atoms to Fe[B] atoms, leading to a change of chemical environment and magnetic anisotropy. Then a further increase in the fraction of Mn atoms tends to occupy the Fe[A, C] atoms and causes some Mn[B] moments to cant to the direction of the average magnetization, resulting the coexistence and competition between the ferromagnetic and antiferromagnetic interactions.The measurement of transport properties shows that Fe3-xMnxSi epitaxial films exhibit metallic conductivity characteristics at x ?0.8, which meet the phonon-phonon scattering mechanism at high temperatures and the non-traditional single-magnon scattering mechanism at low temperatures. At x=1.0, a metal-semiconductor crossover occurs. The above phenomena can be attributed to the disruption of local symmetry as well as the increasing disorder due to the enhanced ferromagnetic and antiferromagnetic interaction.The saturation magnetization and coercivity of the Fe3-xCoxSi epitaxial films gradually increase with the increasing Co content. The residual resistivity decreases with the increasing Co content, while the contribution of skew scattering to the anomalous Hall effect reduces. This is because that the increase of Co atoms reduces the disordered Fe-Fe and Co-Fe antisite defects in the Fe3-xCoxSi films, resulting in the decrease of residual resistivity and the scattering of impurities or defects.