The temperature dependence of the isothermal magnetic entropy change, ΔS_M, and the magnetic field dependence of the refrigerant capacity, RC, have been investigated in a composite system xA + (1 − x)B, based on Fe₈₇Zr₆B₆Cu₁ (A) and Fe₉₀Zr₈B₂ (B) amorphous ribbons. Under a magnetic field change of 2 T, the maximum improvement of the full-width at half maximum of ΔS_M(T) curve (47% and 29%) and the RC (18% and 23%), in comparison with those of the individual alloys (A and B), is observed for x ≈ 0.5. Moreover, a flattening over 80 K in the ΔS_M(T) curve around room temperature range is observed, which is a key feature for an Ericsson magnetic refrigeration cycle.

The Heusler alloy ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{37}{\mathrm{Sn}}_{13}$ was successfully produced as ribbon flakes of thickness around $7–10\mu \mathrm{m}$ melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be $M_S=218\mathrm{K}$ , $M_f=207\mathrm{K}$ , $A_S=224\mathrm{K}$ , and $A_f=232\mathrm{K}$ ; the thermal hysteresis of the transformation is $15\mathrm{K}$ . Ferromagnetic $L{2}_1$ bcc austenite phase shows a Curie point of $313\mathrm{K}$ , with cell parameter $a=0.5971\left(5\right)\mathrm{nm}$ at $298\mathrm{K}$ , transforming into a modulated $7M$ orthorhombic martensite with $a=0.6121\left(7\right)\mathrm{nm}$ , $b=0.6058\left(8\right)\mathrm{nm}$ , and $c=0.5660\left(2\right)\mathrm{nm}$ , at $150\mathrm{K}$ .

Combining different experimental techniques, investigations in hexagonal $P{6}_3/mmc$ Er${}_2$Fe${}_{17}$ show remarkable magnetovolume anomalies below the Curie temperature, $T_C$. The spontaneous magnetostriction reaches $1.6\times {10}^{-2}$ at 5 K and falls to zero well above $T_C$, owing to short-range magnetic correlations. Moreover, Er${}_2$Fe${}_{17}$ exhibits direct and inverse magnetocaloric effects (MCE) with moderate isothermal magnetic entropy $\Delta S_M$, and adiabatic temperature $\Delta T_{\mathrm{ad}}$ changes [$\Delta S_M\sim -4.7$ J(kgK)${}^{-1}$ and $\Delta T_{\mathrm{ad}}\sim 2.5$ K near the $T_C$, and $\Delta S_M\sim 1.3$ J(kgK)${}^{-1}$ and $\Delta T_{\mathrm{ad}}\sim -0.6$ K at 40 K for $\Delta H=80$ kOe, respectively, determined from magnetization measurements]. The existence of an inverse MCE seems to be related to a crystalline electric field-level crossover in the Er sublattice and the ferrimagnetic arrangement between the magnetic moments of the Er and Fe sublattice. The main trends found experimentally for the temperature dependence of $\Delta S_M$ and $\Delta T_{\mathrm{ad}}$ as well as for the atomic magnetic moments are qualitatively well described considering a mean-field Hamiltonian that incorporates both crystalline electric field and exchange interactions. $\Delta S_M\left(T\right)$ and $\Delta T_{\mathrm{ad}}\left(T\right)$ curves are essentially zero at $\sim$150 K, the temperature where the transition from direct to inverse MCE occurs. A possible interplay between the MCE and the magnetovolume anomalies is also discussed.