Large magnetocaloric effect in chromium dioxide with second-order phase transition

Abstract

A magnetic entropy change of 25.4 mJ cm−3 K−1 at H = 1.5 T in CrO2 nano-rods is observed, which is one of the largest magnetocaloric effects ever reported among those oxides. In this work, a molecular field model, Landau theory and Debye approximation are used to unveil the origins of the magnetic entropy change associated with a second phase transition in the system. The theoretical estimates indicate that the entropy change results mainly from a field-induced spin ordering, whereas the lattice entropy contribution is approximately 0.112–0.335 mJ cm−3 K−1. Finally, the electronic entropy change is considered to be negligible. The work is of significance not only in the understanding of the magnetic oxide refrigerant with large magnetic entropy change but also in the exploitation of a new class of potential magnetic refrigerants with large magnetostriction.