Realization of small intrinsic hysteresis with large magnetic entropy change in La_0.8Pr_0.2(Fe_0.88Si _0.10Al_0.02)₁₃ by controlling itinerant-electron characteristics

Tuning of phase-transition characteristics in La(Fe_xSi _1-x)₁₃ was conducted in view of the correlation between microscopic itinerant electron natures and macroscopic thermodynamic (magnetocaloric) quantities. To realize a small hysteresis loss Q_H accompanied by a large magnetic entropy change ΔS_M in La(Fe_xSi_1-x)₁₃, two types of modulation based on itinerant electron characteristics, namely, the Fermi-level shift and the magnetovolume effect were combined by complex partial substitution of Al and Pr. Ab-initio calculations predict the reduction of a transition hysteresis owing to the Fermi-level shift after partial substitution of Al. On the other hand, the chemical pressure arisen from partial substitution of Pr enhances ΔS_M through magnetovolume effect. The selective enhancement of ΔS_M apart from Q_H by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ΔS _M of La_0.8Pr_0.2(Fe_0.88Si _0.10Al_0.02)₁₃ is -18 J/kg K under a magnetic field change of 0-1.2 T, while the maximum value of Q_H becomes 1/6 of that for La(Fe_0.88Si_0.12)₁₃.