Effect of Mn substitution on the magnetic and magneto-transport properties of Fe3−xMnxSi (0 ≤ x ≤ 1.25) alloys

Effect of partial Mn substitution for Fe in Fe3Si on the structural, magnetic, transport, and magnetotransport properties has been studied. Mn substitution is found to induce a re-entrant antiferromagnetic phase at low temperatures. The increase in the antiferromagnetic exchange causes a gradual decrease in the Curie temperature and the saturation magnetization. Temperature dependence of the electrical resistivity data shows that the high temperature resistivity is dominated by electron-phonon scattering, while below the re-entry temperature (TR), electron-magnon scattering is dominant. These results are in agreement with the reported spin polarization studies and indicate that the reentrant behavior is detrimental to half metallicity. Application of a field causes negative magnetoresistance (MR) above TR. However, at 5 K, the magnetoresistance is found to be positive, with the magnitude increasing with x. For x > 0.8, field induced irreversibility has been found in MR vs. field isotherms at 5 K, which indicates that the re-entrant phase has competing magnetic interactions. Canted magnetic structure known to exist in this system is assumed to be responsible for this anomalous behaviour.