Hyperfine interactions and band structures of LaFe13−xSix intermetallic compounds with large magnetic entropy changes

Magnetic properties and hyperfine interactions of LaFe13−xSix intermetallic compounds with large magnetic entropy changes were investigated by means of Mössbauer spectroscopy, band structure calculation and magnetization measurements. It was found that the 57Fe magnetic hyperfine field at FeI (8b) site is larger than that at the FeII (96i) site, whereas the magnetic moment of Fe atoms at the FeI site is smaller than that of Fe atoms at the FeII site. The temperature dependence of the average 57Fe magnetic hyperfine field was found to deviate from the mean field model close to TC, implying that the first-order magnetic phase transition is predominant in the sample of LaFe11.7Si1.3, and consequently results in a large magnetic entropy change. Furthermore, the effect of Si substitution for Fe on hyperfine parameters was investigated.