Changes in electronic states and magnetic free energy in La_1−zCe_z(Fe_xSi_1−x)₁₃ magnetic refrigerants

Abstract

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.

High-temperature phase transition and magnetic property of LaFe11.6Si1.4 compound

“…Those compounds undergo a first-order magnetic transition at T C about 200 K, and an itinerant-electron metamagnetic (IEM) transition just above T C [2,3], which result in a large magnetocaloric effect (MCE). Because of the low price of starting materials and excluding deleterious elements, LaFe 13−x Si x compounds are the hot research points in magnetic refrigerant materials field for long time [4][5][6][7][8][9]. Recently, the main studies about LaFe 13−x Si x compounds focused on how to enhance T C , improve magnetocaloric properties, reduce the large thermal and magnetic hysteresis, and improve the corrosion resistant property.…”

Tuning the Magnetocaloric Properties of the La(Fe,Si)13 Compounds by Chemical Substitution and Light Element Insertion

“…They found a decrease of the unit cell parameter and ∆S max M with an increasing Nd content. Fujita et al [57,58] and Fujieda et al [59,60] studied the effect of partial substitution of La in La(Fe 0.88 Si 0.12 ) 13 compound. Figure 7 (Left) shows that the unit cell parameter and T C linearly decrease with Ce/Pr content; these results were mainly attributed to the magnetovolume effect [59,60].…”

Enhancing ferromagnetism in the kinetically arrested LaFe12B6 by partial La/Nd substitution

“…Together with the introduction of 4f electrons into the itinerant-electron LaFe12B6, these changes may adjust critical fields of both AFM-FM and PM-FM transitions. [32][33][34][35][36][37] It has been reported that partial substitutions of La by Ce promote ferromagnetic state and increase the temperature of the magnetic field-induced PM-FM transition temperature compared to the unsubstituted LaFe12B6 parent. [38] In this work, we report the effect of Nd on the magnetic properties and magnetocaloric effect of the La0.9Nd0.1Fe12B6 compound, where 10 at.% of 4f 0 La has been replaced with 4f 3 Nd.…”