Magnetocaloric effects in RCo2 compounds

Magnetisation isotherms were measured For a number of (R, R')Co-2 and (R, Y)Co-2 (R, R' = rare earths) compounds. A metamagnetic transition is observed just above the Curie temperature (T-C) of compounds having a first-order phase transition, Le, ErCo2, HoCo2 and (Dy, Y)Co-2. The magnetic entropy change DeltaS(m) shows a largest value of -11.8 J/mol K at 35 K for ErCo2 and it decreases exponentially with increasing temperature. The obtained thermal variation of DeltaS(m) is compared to that of RAI(2) and other intermetallic compounds, Giant magnetocaloric effects observed in RCo2-based compounds are discussed in terms of the 4f(R)-localised spin. 3d(Co)-spin fluctuations as well as nature of the phase transition. (C) 2002 Elsevier Science B.V. All rights reserved.