No abstract

No abstract

Macroscopic anisotropy of spatial selectivity in magnetic nucleation and growth was clarified for itinerant-electron metamagnetic transition of La(Fe0.88Si0.12)13 by the time-dependent Ginzburg-Landau model combined with the Maxwell electromagnetic equation. Spontaneous generation of voltage supports symmetric growth in the longitudinal direction of the specimen as predicted by the simulation. The difference between nucleation-growth behaviors in thermally induced transition and those in field-induced transition is also elucidated. Electrical resistivity measurements also detect anisotropic growth of the induced phase. These results imply that the magnetic-dipole version of Gibbs-Thomson effect governs growth behavior.

No abstract

Tuning of phase-transition characteristics in La(FexSi1−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 QH accompanied by a large magnetic entropy change ΔSM in La(FexSi1−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 ΔSM through magnetovolume effect. The selective enhancement of ΔSM apart from QH by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ΔSM of La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 is −18 J/kg K under a magnetic field change of 0–1.2 T, while the maximum value of QH becomes 1/6 of that for La(Fe0.88Si0.12)13.