Abstract
The structural, magnetic and electron-transport properties of Co2Ti1−xFexSi (x = 0, 0.25, 0.5) ribbons prepared by arc-melting and melt-spinning were investigated. The rapidly quenched Co2Ti0.5Fe0.5Si crystallized in the cubic L21 structure whereas Co2Ti0.75Fe0.25Si and Co2TiFe0Si showed various degrees of B2-type disorder. At room temperature, all the samples are ferromagnetic, and the Curie temperature increased from 360 K for Co2TiSi to about 800 K for Co2Ti0.5Fe0.5Si. The measured magnetization also increased due to partial substitution of Fe for Ti atoms. The ribbons are moderately conducting and show positive temperature coefficient of resistivity with the room temperature resistivity being between 360 μΩcm and 440 μΩcm. The experimentally observed structural and magnetic properties are consistent with the results of first-principle calculations. Our calculations also indicate that the Co2Ti1−xFexSi compound remains nearly half-metallic for x ≤ 0.5. The predicted large band gaps and high Curie temperatures much above room temperature make these materials promising for room temperature spintronic and magnetic applications.
Highlights
Half-metals with the metallic electronic band structure for one spin channel and an insulating band structure for the opposite spin channel are of special interest because they are expected to produce an electron current of only one spin orientation i.e., show nearly 100% transport spin-polarization
Some weak impurity peaks have been detected in these samples and we carried out the Rietveld analysis of the x-ray diffraction (XRD) patterns of all three samples in order to quantify them
XRD analysis shows that the rapidly quenched Co2Ti0.5Fe0.5Si crystallized in the cubic L21 structure whereas Co2Ti0.75Fe0.25Si and Co2TiFe0Si showed various degrees of B2-type disorder
Summary
Magnetic materials including half-metallic ferro-, ferri-, and antiferromagnets that conduct electrons of only one spin channel have recently attracted a lot of attention due to their potential for spintronic devices.[1,2,3,4,5,6] Half-metals with the metallic electronic band structure for one spin channel and an insulating band structure for the opposite spin channel are of special interest because they are expected to produce an electron current of only one spin orientation i.e., show nearly 100% transport spin-polarization. Recent theoretical and experimental investigations have indicated that some Co-based Heusler alloys including Co2MnSi, Co2FeSi, Co2FeAl have shown half-metallic band properties with high Curie temperature much above room temperature, making them potential candidates for room temperature spintronic applications.[7,8,9,10] One of the issues with these materials is the difficulty of synthesizing them in completely ordered L21 structures. Certain types of structural disorder are detrimental to half-metallic properties.[11] Further, for the robustness of half-metallic properties the materials need to have large band gap. These considerations stimulated this work where we aimed to synthesize Co2TiSi, which has been predicted to be half metallic with large band gap of 0.621 eV, 2158-3226/2017/7(5)/055812/6
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