Band Structure Calculations and Magnetic Properties of HoCo3−xSix Compounds

The structural and magnetic properties and band structure results of HoCo3−xSix compounds are reported. First-principles GGA+U+SO calculations, compared with magnetometry experiments, provide deep insight on the magnetic properties of the HoCo3 compound. They show that HoCo3 is a robust ferrimagnet, with strongly localized Ho-4f moments in excellent agreement with neutron data and itinerant Co-3d magnetism, where inclusion of the interstitial contribution brings the Co moments into very good agreement with the experimental data. The electronic structure reveals sharp Ho-4f states well below EF, exchange-split Co-3d bands crossing EF, and noticeable Ho-5d–Co-3d hybridization that mediates the antiparallel Ho–Co coupling and explains the non-negligible interstitial moment, providing a consistent microscopic picture that supports the experimentally observed increase in magnetization upon Co-Si substitution. Metamagnetic transitions are shown in magnetization isotherms. The observed transitions are broad and can be explained by the distribution of internal magnetic fields which arises from differences in the local environments of cobalt atoms. The magnetic properties were correlated with the theoretical results. Two transitions were revealed below room temperature, one due to a transition to a noncollinear magnetic structure and the other due to a temperature-induced metamagnetic transition.