Giant magnetocaloric effect has been observed in ErRu2Si2, which is associated with field-induced metamagnetic transition from antiferromagnetic to ferromagnetic state. The maximum values of magnetic entropy change (−ΔSMmax) and adiabatic temperature change (ΔTadmax) for a field change of 7T are evaluated to be 19.3J∕kgK and 15.9K, respectively, around 5.5K within the temperature range of 4–25K. The value of ΔTadmax is even larger than other potential magnetic refrigerant materials reported in the same temperature range and also comparable to room temperature giant magnetocaloric materials exhibiting first-order magnetic transition from paramagnetic to ferromagnetic state.

Magnetic and structural transitions were found to coincide by substituting Cu for Mn in Mn1−xCuxCoGe, leading to a giant magnetocaloric effects associated with the first-order magnetostructural phase transition from the ferromagnetic to paramagnetic state. Maximum magnetic entropy changes of −ΔSM = 52.5 and 53.3 J/kg K for a magnetic field change of ΔH = 5 T have been observed at 302 and 316 K, for x = 0.080 and 0.085, respectively. The giant magnetocaloric effects with tunable phase transition temperatures through subtle variations in composition make this system promising for room-temperature magnetic cooling applications.

Phase diagram and magnetocaloric effects in Ni50Mn35(In1−xCrx)15 and (Mn1−xCrx)NiGe1.05 alloys J. Appl. Phys. 115, 17A922 (2014); 10.1063/1.4866082 Magnetostructural transition and magnetocaloric effect in MnNiGe1.05 melt-spun ribbonsThe thermomagnetic and magnetocaloric properties of the MnNiGe 1Àx Al x system have been investigated by magnetization and differential scanning calorimetry (DSC) measurements. The presence of first-order magnetostructural transitions (MSTs) from hexagonal ferromagnetic to orthorhombic antiferromagnetic phases has been detected for x ¼ 0.085 and 0.09 at 193 K and 186 K, respectively. The values of latent heat (L ¼ 6.6 J/g) and corresponding total entropy changes (DS T ¼ 35 J/kg K) have been evaluated for the MST (x ¼ 0.09) from DSC measurements. The magnetic entropy change for x ¼ 0.09 (DS M ¼ 17.6 J/kg K for 5 T) was found to be comparable with well-known giant magnetocaloric materials, such as Gd 5 Si 2 Ge 2 , MnFeP 0.45 As 0.55 , and Ni 50 Mn 37 Sn 13 .

Giant magnetocaloric effect in antiferromagnetic borocarbide superconductor RNi2B2C (R=Dy, Ho, and Er) compounds J. Appl. Phys. 110, 043912 (2011); 10.1063/1.3625250The hydrogen absorption properties and magnetocaloric effect of La0.8Ce0.2(Fe1−xMnx)11.5Si1.5Hy

Nanocrystalline Pr0.65(Ca0.7Sr0.3)MnO3 show large magnetocaloric effect at their charge order transition temperature (TCO) as well as at the temperature at which the spontaneous destabilization of charge ordered state occurs (TM). In comparison to their polycrystalline bulk form, TM’s are substantially enhanced in the cases of nanocrystalline samples, whereas their TCO’s remain almost unchanged. Although there is no clear signature of charge order transition in the temperature dependence of magnetic susceptibility and resistivity for the sample with the lower particle size, a clear maxima due to charge order transition is visible in its temperature dependence of change in magnetic entropy.

(MnNiSi)1−x(FeCoGe)x undergoes a magnetostructural phase transition near room temperature that is acutely sensitive to applied hydrostatic pressure, which presents as a marked shift in the martensitic transition temperature (TM) by about –7.5 K/kbar. The magnetostructural transition can therefore be induced by applied hydrostatic pressure or by magnetic field. The barocaloric and magnetocaloric effects were measured across TM (for the sample with x = 0.38), and the corresponding entropy changes were +74 J/kg K (P = 2.7 kbar) and –58 J/kg K (μ0 H = 5 T), respectively. It was observed that the transition entropy change increases with pressure, which results in an enhancement of the barocaloric effect. Our measurements show that the transformed phase fraction associated with magnetostructural transition does not depend on pressure and, therefore, this enhancement cannot be attributed to a pressure-assisted completion of the phase transformation.

Some recent experimental studies show the invisibility of antiferromagnetic transition in the cases of manganites when their particle size is reduced to nanometer scale. In complete contrast to these cases, we have observed the signature of antiferromagnetic transition in the magnetocaloric properties of nanocrystalline La 0.125 Ca 0.875 MnO 3 of average particle size 70 and 60 nm similar to its polycrystalline bulk form. The system exhibit inverse magnetocaloric effect in its polycrystalline and nanocrystalline form. An extra ferromagnetic phase is stabilized at low temperature for the sample with particle size ∼ 60 nm.

A comprehensive study of the temperature (T) and magnetic field (H) dependence of magnetic entropy change (ΔS M) for different materials exhibiting inverse magnetocaloric effect (IMCE) is reported. We show that ΔS M follows a power law dependence of H (ΔS M ∼ H n , n is an exponent) for these compounds. In contrast to conventional magnetocaloric effect (CMCE), n is independent of H and T in the case of IMCE. As a result, a universal master curve can be constructed to describe ΔS M (T) of the IMCE systems for different H without rescaling temperature axis. This is completely different from that reported for CMCE, where the rescaling of temperature axis with the introduction of at least one reference temperature is needed for constructing a universal curve. The different universal behavior of IMCE is attributed to the constant value of n in any field and temperature, which is a generic feature of IMCE systems irrespective of their magnetic state and nature of phase transition. From the proposed phenomenological universal curve, one can extrapolate the magnetocaloric properties of IMCE systems in any temperature and magnetic field range, which would be helpful in designing controlled active magnetic refrigeration devices.