Magnetocaloric effect in the vicinity of the magnetic phase transition in NdCo2−xFex compounds

In the present paper, the magnetocaloric effect (MCE) of ${\mathrm{NdCo}}_{2\ensuremath{-}x}{\mathrm{Fe}}_{x}$ ($x\phantom{\rule{0.28em}{0ex}}=\phantom{\rule{0.28em}{0ex}}0$, 0.2, 0.4, 0.6) compounds was investigated by magnetization measurements. The temperature-dependent high-resolution synchrotron x-ray diffraction study shows a magnetostructural transition from the paramagnetic cubic phase to the ferromagnetic tetragonal phase below their Curie temperatures. Differential scanning calorimetry analysis shows the absence of thermal hysteresis, indicating the second-order nature of the magnetostructural phase transition in these compounds. The maximum values of magnetic entropy change ($\mathrm{\ensuremath{\Delta}}{S}_{M}$) and wide operating temperature (OT) are obtained under a field change of 5 T, which are 7.33 ${\mathrm{Jkg}}^{\ensuremath{-}1}{\mathrm{K}}^{\ensuremath{-}1}$, 6.45 ${\mathrm{Jkg}}^{\ensuremath{-}1}{\mathrm{K}}^{\ensuremath{-}1}$, 5.71 ${\mathrm{Jkg}}^{\ensuremath{-}1}{\mathrm{K}}^{\ensuremath{-}1}$, 4.70 ${\mathrm{Jkg}}^{\ensuremath{-}1}{\mathrm{K}}^{\ensuremath{-}1}$ and 78 K, 82 K, 85 K, 92 K for $x$ = 0, 0.2, 0.4, and 0.6, respectively. The corresponding values of relative cooling power (RCP) are 529.96 ${\mathrm{Jkg}}^{\ensuremath{-}1}$, 497.25 ${\mathrm{Jkg}}^{\ensuremath{-}1}$, 470.55 ${\mathrm{Jkg}}^{\ensuremath{-}1}$, and 428.31 ${\mathrm{Jkg}}^{\ensuremath{-}1}$. The observed wide OT range and large RCP values are comparable with Gd, ${\mathrm{Gd}}_{5}{\mathrm{Ge}}_{2}{\mathrm{Si}}_{2}$, and some rare-earth-based giant magnetocaloric materials, making this series of compounds suitable for magnetic refrigeration.