Magnetic and magnetothermal properties of Nd(Co$_{1-x}$Fe$_x$)$_2$ ($x\leq 0.16$) compounds

We present the results of measurements of the specific magnetization, high-field susceptibility, and magnetocaloric effect (MCE) of Nd(Co$_{1-x}$Fe$_x$)$_2$ compounds when Co is replaced by Fe in the concentration range $x = 0$–$0.16$. The phase composition was controlled by X-ray structural analysis. MCE was studied in the temperature range $5$–$320$ K in magnetic fields up to $7200$ kA/m based on the calculation of the magnetic entropy change ($\Delta S_m$). It was found that, in contrast to the table-like dependences of the MCE in $R$(Co-Fe)$_2$ compounds with heavy rare-earth metals ($R$), for the presented samples there are two separate peaks of $\Delta S_m(T)$, the first one in the vicinity of the Curie temperature, the second one in the vicinity of the spin-reorientation transition. In addition, for all studied compounds, a reverse MCE was found at temperatures below the spin-reorientation transition.