Magnetisation isotherms were measured for a number of (R, R′)Co₂ and (R, Y)Co₂ (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, i.e. ErCo₂, HoCo₂ and (Dy, Y)Co₂. The magnetic entropy change ΔS_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 ΔS_m is compared to that of RAl₂ 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. © 2002 Elsevier Science B.V. All rights reserved.

Duc N.H., Anh D.T.K.

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Từ khóa : Magnetic hysteresis; Magnetization; Metamagnetism; Phase transitions; Transition metal compounds; Magnetocaloric effects; Rare earth compounds