Magnetocaloric effect in PMN-PT/CFO multiferroic magnetoelectric composite

Magnetocaloric effect (MCE) is the heating or the cooling of magnetic material when subject to a magnetic field changes. This effect is being studied as an environmental-friendly alternative for reducing greenhouse emission and improved efficiency for small to medium load cooling requirements. In particular, caloric effects in ferroic solids are described as a reversible isothermal entropy change or adiabatic temperature change obtained upon the application of a suitable external stimulus. Any material system, when acted upon by an adiabatic stimulus, can generate a non-dissipative temperature change. Although many efforts have been made to increase the efficiency of the MCE, its practical application still far from done. In this sense, multiferroic (MF) materials are the subject of intense research as they are good candidates for novel applications such as photovoltaics, magnetic cooling, energy harvesting, etc. In these materials, the as known as multicaloric effect is defined as the adiabatic reversible temperature change activated by electric or magnetic fields.
It's known that the multicaloric effect in multiferroics may induce temperature changes significantly greater to those achieved in the existing magnetocaloric or electrocaloric effects. As an example of multicaloric materials are the single-phase multiferroic Y$_{2}$CoMnO$_{6}$ and the composite Gd$_{5}$(Si,Ge)$_{4}$/PVDF. In particular, the multicaloric effect in the composites is very interesting since its possible to combine different phases and optimize its efficiency. In this work, we present the magnetocaloric effect of the multiferroic composite PMN-PT/CoFe$_{2}$O$_{4}$ at different temperatures and compare to the magnetocaloric effect of pure CoFe$_{2}$O$_{4}$ (CFO).
The multiferroic composite PMN-PT/CFO of 0–3 connectivity was prepared by the conventional solid-state reaction with a stoichiometric ratio of 80\% of PMN-PT and 20\% CFO. The magnetic characterization was carried out using a MPMS3 SQUID magnetometer by Quantum Design. The results show a relevant change in the entropy for the PMN-PT/CFO composite compared with the pure CFO. This difference in the entropy between the two samples can be related to the multicaloric effect. For the composite, there is a contribution from the electrocaloric effect of the ferroelectric phase due to the magnetoelectric coupling. Therefore, the use of multiferroics materials is a good way to increase the efficiency of magnetocaloric devices.