Recent progress on caloric effects are reviewed. The application of external stimuli such as magnetic field, hydrostatic pressure, uniaxial stress and electric field give rise respectively to magnetocaloric, barocaloric, elastocaloric and electrocaloric effects. The values of the relevant quantities such as isothermal entropy and adiabatic temperature-changes are compiled for selected materials. Large values for these quantities are found when the material is in the vicinity of a phase transition. Quite often there is coupling between different degrees of freedom, and the material can exhibit cross-response to different external fields. In this case, the material can exhibit either conventional or inverse caloric effects when a field is applied. The values reported for the many caloric effects at moderate fields are large enough to envisage future application of these materials in efficient and environmental friendly refrigeration.

Magnetic refrigeration relies on a substantial entropy change in a magnetocaloric material when a magnetic field is applied. Such entropy changes are present at first‐order magnetostructural transitions around a specific temperature at which the applied magnetic field induces a magnetostructural phase transition and causes a conventional or inverse magnetocaloric effect (MCE). First‐order magnetostructural transitions show large effects, but involve transitional hysteresis, which is a loss source that hinders the reversibility of the adiabatic temperature change ΔT_ad. However, reversibility is required for the efficient operation of the heat pump. Thus, it is the mastering of that hysteresis that is the key challenge to advance magnetocaloric materials. We review the origin of the large MCE and of the hysteresis in the most promising first‐order magnetocaloric materials such as Ni–Mn‐based Heusler alloys, FeRh, La(FeSi)₁₃‐based compounds, Mn₃GaC antiperovskites, and Fe₂P compounds. We discuss the microscopic contributions of the entropy change, the magnetic interactions, the effect of hysteresis on the reversible MCE, and the size‐ and time‐dependence of the MCE at magnetostructural transitions.

We study the structural and magnetic properties of Heusler based Ni₅₀Mn_50−x Sb _x in the composition range 5.0 ≤ x ≤ 25.0. The cubic phase is preserved in the range 17.0 ≤ x ≤ 25.0, and the presence of martensitic transformations are found in alloys with x ≤ 15.0. In a critical composition range 12.5 ≤ x ≤ 10.0, the magnetic coupling in both austenitic and martensitic phases is paramagnetic, however, the presence of antiferromagnetic short-range correlations is observed in both phases. We discuss the consequences of these correlations on the behavior of the magnetic moment with respect to electronic properties.

Mn_2−xCr_xSb exhibits an antiferromagnetic-ferrimagnetic transition of which the temperature can be changed by controlling the Cr concentration. Increasing the Cr content from x = 0.05 to 0.13 raises the transition temperature from about 180 K up to around room temperature. To suppress the inevitable ferromagnetic MnSb impurity phase, we partially replace Sb by In. Mn_2−xCr_xSb_1−yIn_y alloys have an antiferromagnetic-ferrimagnetic transition and a narrow transition hysteresis and exhibit the inverse magnetocaloric effect. We examine the magnetocaloric effect from the magnetization and direct adiabatic temperature-change measurements.

The present study on magnetic and structural properties of Ni₅₀Mn₄₅Ga₅ confirms that structural metastability is an inherent property of Ni₅₀Mn_50–xX_x Heusler alloys with X as In, Ga, and Sn. The ternary alloy transforms during temper-annealing into a dual-phase composite alloy. The two phases are identified to be cubic L2₁, Ni₅₀Mn₂₅Ga₂₅, and tetragonal L1₀ Ni₅₀Mn₅₀. Depending on the annealing temperature, the magnetic-proximity effect giving rise to shell-ferromagnetism has been observed when annealing is carried out under an external magnetic field. The upper and lower remanence values $M_R^{+}$ and $M_R^{-}$ have the same sign even at high temperatures. Such alloys can be promising candidates for heat- and magnetic-field-resistant magnetic recording media.