First-order phase transitions are accompanied by a latent heat. Consequently, manipulating them by means of an external field causes a caloric effect. Although transitions from antiferromagnetic to paramagnetic states are not controlled by a magnetic field, a large barocaloric effect is expected when strong cross-correlations between the volume and magnetic order occur. Here we examine how geometric frustration in itinerant antiferromagnetic compounds can enhance the barocaloric effect. We study the thermodynamic behaviour of the frustrated antiferromagnet Mn3GaN, and report an entropy change of 22.3 J kg(-1) K(-1) that is concomitant with a hydrostatic pressure change of 139 MPa. Furthermore, the calculated value of the adiabatic temperature change reaches 5 K by depressurization of 93 MPa. The giant barocaloric effect in Mn3GaN is caused by a frustration-driven enhancement of the ratio of volume change against the pressure coefficient of the Néel temperature. This mechanism for enhancing the barocaloric effect can form the basis for a new class of materials for solid-state refrigerants.

Role of joule heating effect and bulk-surface phases in voltage-driven metal-insulator transition in VO2 crystalThe VO2 interface, the metal-insulator transition tunnel junction, and the metal-insulator transition switch On-Off resistance Geometric confinement effects on the metal-insulator transition temperature and stress relaxation in VO2 thin films grown on silicon

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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.

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