Electron doping in the ferromagnetic and metallic double perovskites ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ is achieved via the partial substitution of ${\mathrm{Sr}}^{2+}$ by ${\mathrm{La}}^{3+}.$ We show that this doping promotes an extraordinary rising of the Curie temperature of about 70 K above that of the pristine compound. This finding reveals that the ferromagnetic coupling is mediated by itinerant carriers, thus providing solid experimental support to the double-exchange picture for the magnetic interactions. The observation that $T_C$ can be substantially enhanced may be of relevance for technological applications of these materials in advanced spin devices.

We report on calorimetry under applied hydrostatic pressure and magnetic field at the antiferromagnetic-ferromagnetic (AFM/FM) transition of ${\mathrm{Fe}}_{49}{\mathrm{Rh}}_{51}$. Results demonstrate the existence of a giant barocaloric effect in this alloy, a functional property that adds to the magnetocaloric and elastocaloric effects previously reported for this alloy. All caloric effects originate from the AFM/FM transition which encompasses changes in volume, magnetization, and entropy. The strong sensitivity of the transition temperatures to both hydrostatic pressure and magnetic field confers to this alloy outstanding values for the barocaloric and magnetocaloric strengths ($|$\Delta${}S|$/$$\Delta${}p$ $$\sim${}$ 12 J kg${}^{$-${}1}$K${}^{$-${}1}$kbar${}^{$-${}1}$ and $|$\Delta${}S|$/${$\mu${}}_{0}$\Delta${}H$ $$\sim${}$ 12 J kg${}^{$-${}1}$K${}^{$-${}1}$T${}^{$-${}1}$). Both barocaloric and magnetocaloric effects have been found to be reproducible upon pressure and magnetic field cycling. Such a good reproducibility and the large caloric strengths make Fe-Rh alloys particularly appealing for solid-state cooling technologies at weak external stimuli.