Giant multicaloric response of bulk Fe49Rh51

Abstract

We report on the multicaloric response of the Fe 49 Rh 51 alloy under the combined application of hydrostatic pressure and magnetic field. Experimental data are complemented by a mean field model that takes into account the interplay between structural and magnetic degrees of freedom. A large multicaloric strength has been found for this alloy, and it is shown that a suitable combination of pressure and magnetic field enables the sign of the entropy change to be reversed and thus the multicaloric effect can be tuned from conventional to inverse. It is also shown that an extended temperature window for the multicaloric effect can be achieved by taking advantage of the coupling between structure and magnetism which enables a cross response of the alloy under the application of different external fields. Mean field calculations remarkably reproduce experimental results.

The La(Fe,Mn,Si)13Hz magnetic phase transition under pressure

“…Stern‐Taulats et al demonstrate that if we assume no change in magnetization or material compressibility with pressure at the maximum or zero field positions (where in our cycle the pressure changing steps take place), the energy loss in a field‐pressure full multicaloric cycle can be approximated as Δ p Δ V . In this case the cross‐susceptibility χ 12 terms represent the contribution from the change in M due to p and the change in V due to H . If a multicaloric cycle is executed as follows: (i) apply the magnetic field in 0 GPa; (ii) increase the pressure to 0.02 GPa; (iii) remove the magnetic field in 0.02 GPa; (iv) return the pressure to zero, we observe a greatly decreased magnetic hysteresis indicated by the striped areas in Fig.…”

The Giant Elastocaloric Effect in a Cu–Zn–Al Shape‐Memory Alloy: a Calorimetric Study

“…Up to now, there are no calorimetric techniques capable of operating under applied uniaxial stress, which is of special interest for an accurate characterization of Δ S . With regards to the multicaloric effects, scarce experimental data have been reported among all the families of caloric materials and the estimates usually rely on indirect methods or first‐principle calculations . Hence, there is a need for the development of novel setups which provide calorimetric input for the characterization of elastocaloric effects, as well as for experimental data on multicaloric effects driven by more than one field.…”

Contributions to Hysteresis in Magnetocaloric Materials

“…Note that in systems where there are competing exchange interactions, hydrostatic pressure can strengthen one interaction over another, and a simple rule of thumb cannot be used to predict the impact that it will have on the transitional properties. Although hydrostatic pressure has been introduced in multicaloric cycles to cancel the hysteresis in the magnetic cycle, once the cross terms are taken into account it be shown that the loss is transfered instead into the pressure cycle. Note that there can be other advantages to introducing hydrostatic pressure into the cooling cycle beyong controlling hysteretic loss …”