Structure, magnetic properties and electrical resistivity of Co2FeSi1−xGax Heusler alloy thin films

• A linear dependence of lattice parameter and TC was observed with Ga content.
• Indirect evidence of half-metallicity was examined from resistivity measurements.
• Co2FeSi1−xGax films with higher Ga showed better magnetic and electrical properties.

The influence of Ga on the structural, magnetic and half-metallic properties of Co2FeSi1−xGax (0≤x≤1) thin films grown on Si (100) substrates using ultra high vacuum magnetron sputtering has been systematically investigated. The linear increase in cubic lattice parameter from 5.63 Å to 5.73 Å and the Curie temperature (TC) from 854 K to 941 K with x varying from 0 to 1 indicate the progressive substitution of Ga for Si. The coercivity (Hc) was found to decrease from 26 Oe (x=0) to 3 Oe (x=1) at room temperature and is attributed to the decrease in magnetic anisotropy. The magnetic hysteresis loops measured from 300–873 K revealed that the film where Ga completely replaces Si exhibit better stability in both saturation magnetization (Ms) and Hc with temperature. The increase in coercivity at higher temperatures is attributed to the film to substrate interaction. The measured Ms at 100 K decreases from 5.01 µB/f.u. (x=0) to 4.49 µB/f.u. (x=1) and follows the trend of Slater-Pauling rule. The indirect evidence of half-metallic nature is examined from the temperature dependent electrical resistivity measurements.