The influence of partial substitution of Ce on the electronic structure and magnetic free energy has been investigated for La1−z Ce z (Fe x Si1−x )13. From the Mössbauer spectroscopy of La0.7Ce0.3(Fe0.88Si0.12)13, the distribution of the electric field gradient is found to be scarcely changed, therefore, the volume reduction by partial substitution is regarded as isotropic. The change of the isomer shift to positive sign after the partial substitution is closely correlated with the 5d and/or 4f electrons of Ce. The change in magnetic free energy has been examined for La0.7Ce0.3(Fe0.86Si0.14)13 having a large magnetic entropy change ΔS m and a small hysteretic behaviour. From the results analysed by the Landau expansion theory, the large ΔS m and the small hysteresis of this compound are attributed to the magnitude and thermal variation of the fourth-order Landau coefficient in magnetic free energy. Consequently, the combination of partial substitution and control of Fe concentration is useful for highly efficient magnetic refrigerants.
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Fujita et al. (2011) studied this question.
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