Effect of Ho substitution on structural, magnetic and magnetocaloric properties of Co(CrFe)O4

In this study, structural, magnetic and magnetocaloric properties of Ho-substituted Co(CrFe)O 4 spinel compounds produced by the sol–gel method were investigated. The Ho concentration in Co(CrFe)O 4 spinel structure was changed from 0 to 20% by 5% steps. It is observed that the Ho 3+ ions create a new phase HoCrO 3 /HoFeO 3 in the host spinel lattice. SEM images of samples indicate that the average particle size increases with Ho content. The paramagnetic to ferro-/ferrimagnetic phase transition temperature increases from 312 to 344 K with Ho content. While the fluctuation in saturation magnetization of samples was detected at low temperature, it almost becomes a linear change with the Ho content. The maximum magnetic entropy change under 7 T magnetic field was found as − 1.39, − 1.50, − 1.20, − 0.98 and − 0.91 J/kgK for Ho-free, 5, 10, 15 and 20 wt% Ho content in CoCrFeO 4 spinel structure, respectively.