Pressure-Induced Colossal Magnetocaloric Effect in MnAs

To present day, the maximum magnetocaloric effect (MCE) at room temperature for a magnetic field change of 5 T is $40\mathrm{J}/(\mathrm{k}\mathrm{g}\mathrm{K})$ for MnAs. In this Letter we present colossal MCE measurements on MnAs under pressure, reaching values up to $267\mathrm{J}/(\mathrm{k}\mathrm{g}\mathrm{K})$, far greater than the magnetic limit arising from the assumption of magnetic field independence of the lattice and electronic entropy contributions. The origin of the effect is the contribution to the entropy variation coming from the lattice through the magnetoelastic coupling.

Figure 1

Magnetization curves for as prepared MnAs at a pressure of 1.80 kbar with increasing field and temperature.

Figure 2

The MCE as a function of temperature and pressure for as prepared MnAs.

Figure 3

Experimental maximum $-\Delta S$ values (circles) for MnAs under pressure, and comparison with the theoretical magnetic upper limit value for $J_{\mathrm{e}\mathrm{f}\mathrm{f}}=2$ for the Mn atom.

Figure 4

Comparison of the CMCE for MnAs under pressure with MnAs [14], ${\mathrm{M}\mathrm{n}\mathrm{A}\mathrm{s}}_{0.9}{\mathrm{S}\mathrm{b}}_{0.1}$ [14], ${\mathrm{F}\mathrm{e}\mathrm{M}\mathrm{n}\mathrm{A}\mathrm{s}}_{0.55}{\mathrm{P}}_{0.45}$ [17], and optimally prepared ${\mathrm{G}\mathrm{d}}_5{\mathrm{G}\mathrm{e}}_2{\mathrm{S}\mathrm{i}}_2$ [29]. In the inset, experimental areas under the $-\Delta S$ vs $T$ curves (circles) compared with the calculated ones (dashed line) for MnAs.