MAGNETIC ENTROPY OF FERROMAGNETIC AND ANTIFERROMAGNETIC CE(FE1-XCOX)2

Specific heat and high field magnetization were measured for Ce(Fe1-xCox)2, which shows a double magnetic transition in the concentration range of 0.04<x<0.3. The compounds with 0 less-than-or-equal-to x less-than-or-equal-to 0.3 show a specific heat anomaly due to the ferromagnetic to paramagnetic transition at T(c). Magnetic entropy of CeFe2 was evaluated as 2.5 J/K mol, which is much lower than that expected from a localized moment model. Besides anomaly at T(c), another specific heat anomaly due to the antiferromagnetic (AF) to ferromagnetic (F) transition was observed for x=0.1 and 0.2. It is shown that the entropy change associated with the AF-F transition is mainly described by a difference in the electronic specific heat between the F and AF states. The AF-F transition of Ce(Fe1-xCox)2 is discussed from the thermodynamical point of view.