Enhanced refrigeration capacity in Ho1-xDyxB2 compounds around liquid hydrogen temperature

Abstract

In this study, the crystal structure, magnetic properties, and magnetocaloric effect of Ho1-xDyxB2 compounds were investigated. It was found that nearly single-phase (Ho,Dy)B2 compounds with the AlB2-type structure directly form in the as-arc melted alloys and have two successive magnetic transitions. With the increase of Dy concentration x from 0 to 0.8, the spin reorientation transition temperature remains at about 13 K, while the Curie temperature significantly increases from 16 to 43 K. As a result, the full-width at half-maximum of the magnetic entropy change versus temperature curve increases from 19.9 to 48.2 K. Also, these Ho1-xDyxB2 compounds exhibit a large refrigeration capacity of 523–635 J kg−1 under a magnetic field change of 5 T, although the maximum magnetic entropy change decreases from 34.3 to 17.2 J kg−1 K−1. In addition, Dy-containing compounds exhibit a table-like magnetocaloric effect compared with the HoB2 compound. Our results indicate that Ho1-xDyxB2 compounds are a promising candidate for cryogenic magnetic refrigeration around liquid hydrogen temperature.