The remarkable impact of nitridation temperature on the magnetocaloric effect of CoFe2/MgO matrix

In this study, a phenomenological model is used to predict the magnetocaloric effect (MCE) of two CoFe2/MgO nanocomposite samples exposed to nitridation reactions at nitridation temperatures of 400 and 500 °C (they are indicated as N400 and N500, respectively). The findings show that, within the investigated temperature range, the MCE of the N400 sample is conventional with full-width at half-maximum (δTFWHM\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta {\text{T}}_{{{\text{FWHM}}}}$$\end{document}) of 94 K. The N500 sample does, however, actually contain both inverse and conventional MCE with δTFWHM\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta {\text{T}}_{{{\text{FWHM}}}}$$\end{document} of 71 K and 24 K, respectively. Interestingly, the changing nitridation temperature during sample preparation allows for significant tailoring of the MCE of a CoFe2/MgO nanocomposite sample. The MCE of the N400 and N500 samples, in particular, spans a wide range of temperatures, including room temperature and cryogenic temperatures, making them notable magnetocaloric materials. Consequently, N400 and N500 samples can be used food-refrigeration and liquefying both nitrogen and helium gases.