Magnetic and structural entropy contributions to the multicaloric effects in Ni-Mn-Ga-Cu

We have studied the multicaloric properties of a Ni-Mn-Ga-Cu alloy. In this alloy, application magnetic field and uniaxial stress shift its martensitic transition towards higher temperatures which results in synergic magnetocaloric elastocaloric effects. By proper numerical treatment calorimetric curves obtained under applied we entropy $S(T,{\ensuremath{\mu}}_{0}H,\ensuremath{\sigma})$ as function field, stress, temperature over whole phase space study. determined different contributions to effect noticeably evidenced role played by interplay between vibrational degrees freedom. A comparison single caloric effects shows that appropriate combinations reduce magnitude specific required obtain given value isothermal adiabatic changes. For example, at 299 K, achieve an change ($\mathrm{\ensuremath{\Delta}}S$) $\ensuremath{-}14$ J ${\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$, $\ensuremath{\sim}2.5$ T or 19 MPa are required, while combination dual fields (1 T, 12 MPa) yields same $\mathrm{\ensuremath{\Delta}}S$. Moreover, maximum is enlarged up 9.4 K fields, than ($\ensuremath{\sim}7$ K). The advantage particularly relevant low achievable permanent magnets. Our findings open new avenues for using materials novel refrigeration technologies.