Barocaloric properties of quaternary ${\mathrm{Mn}}_3(\mathrm{Zn},\mathrm{In})\mathrm{N}$ for room-temperature refrigeration applications

The magnetically frustrated manganese nitride antiperovskite family displays significant changes of entropy under hydrostatic pressure that can be useful for the emerging field of barocaloric cooling. Here we show that barocaloric properties of metallic antiperovskite Mn nitrides can be tailored for room-temperature application through quaternary alloying. We find an enhanced entropy change of $|\mathrm{\Delta }{S}_{\mathrm{t}}|=37\mathrm{J}{\mathrm{K}}^{-1}{\mathrm{kg}}^{-1}$ at the $T_t=300\mathrm{K}$ antiferromagnetic transition of quaternary ${\mathrm{Mn}}_3{\mathrm{Zn}}_{0.5}{\mathrm{In}}_{0.5}\mathrm{N}$ relative to the ternary end members. The pressure-driven barocaloric entropy change of ${\mathrm{Mn}}_3{\mathrm{Zn}}_{0.5}{\mathrm{In}}_{0.5}\mathrm{N}$ reaches $|\mathrm{\Delta }{S}_{\mathrm{BCE}}|=20\mathrm{J}{\mathrm{K}}^{-1}{\mathrm{kg}}^{-1}$ in 2.9 kbar. Our results open up a large phase space where compounds with improved barocaloric properties may be found.

Figure 1

(a) Rietveld refinement of powder neutron diffraction data collected at 10 K on banks 1 (backscattering) and 2 (${90}^{\circ }$) of HRPD, ISIS. Black tick marks indicate the reflections from the antiperovskite phase. The minor additional peaks, e.g., at $Q=5.1{\AA }^{-1}$, are from MnO. (b) Temperature dependence of the fitted (100) peak intensity. (c) Thermodiffractogram of the (321) reflection. (d) Temperature dependence of the lattice volume at ambient pressure close to $T_{\mathrm{t}}$ for both the AFM and PM states. (e) Pressure dependence of the lattice volume at 294 K. Dotted vertical lines in (d) and (e) separate the single and mixed phase magnetic regimes, as described in the text. Solid lines in (e) are guides to the eye. Error bars in (d) and (e) are smaller than the symbol size.

Figure 2

(a) Volume change of ${\mathrm{Mn}}_3{\mathrm{Zn}}_{0.5}{\mathrm{In}}_{0.5}\mathrm{N}$ as a function of temperature measured using dilatometry, where $\frac{\mathrm{\Delta }V}{V}$ is calculated from the measured $\frac{dL}{L}$ using $\frac{\mathrm{\Delta }V}{V}=3^{*}\frac{dL}{L}$. (b) Temperature dependent heat flow measurements at normal pressure.

Figure 3

Temperature dependent heat flow measurements measured on (a) cooling and (b) warming at various pressures. Isobaric entropy curves at different applied pressures on (c) cooling and (d) warming, extracted from the data in (a) and (b), respectively. Isothermal entropy change under (e) removal or (f) application of different pressures (BCE). Adiabatic temperature change under (g) removal or (h) application of different pressures.