Tuning of magnetic properties and half-metallicity of electrodeposited Co-Fe-Sn Heusler alloy films by varying elemental composition

Abstract

In an attempt to invoke half-metallicity in non half-metallic Co₂FeSn alloy by bandgap engineering, off-stoichiometric Co_48.5Fe_22.8Sn_28.7 (S1), Co_51.7Fe_21.6Sn_26.7 (S2), and Co_53.8Fe_20.6Sn_25.6 (S3) alloy films were electrodeposited on polycrystalline copper substrate. L2₁-type ordered structure could be achieved in 1400 nm thick films after heat treatment at 550 °C for 1 hour. The processed films exhibited tunable soft ferromagnetic nature with high Curie temperature (∼1100 K) and high effective anisotropy constant (∼10⁶ erg/cc). The magnetic moment of the films varied with composition. Ab initio calculations showed the finite density of states at the Fermi level (E_F) could not be completely suppressed in S1 and S2 alloys, while S3 exhibited a full bandgap in the minority band at E_F. Half-metallic nature of S3 was validated by temperature-dependent electrical resistivity data and Rhodes-Wohlfarth ratio estimated from thermomagnetization measurement. Apart from showcasing a method to induce half-metallicity in these ternary alloy films, this study has identified the Co_53.8Fe_20.6Sn_25.6 alloy film as a promising candidate for spintronic and high-temperature magnetic device applications.