Itinerant electron metamagnetism and a large decrease in the electronic specific heat coefficient of Laves-phase compounds Lu(Co1-xGax)2

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Abstract
High-field magnetization and low-temperature specific heat of the nearly ferromagnetic compounds Lu(Co1-xGax)2 have been investigated. A sharp metamagnetic transition has been observed in these compounds. The critical field Hc decreases with increasing x and becomes lower than 1 T at x=0.12. However, no spontaneous magnetization is confirmed even above x=0.15. With increasing x, the electronic specific heat coefficient gamma increases and reaches 36 mJ K-2 mol-1 for x=0.12 in 0 T, being 1.5 times as large as that of LuCo2. Such a mass enhancement is discussed in terms of the spin fluctuation. The gamma value of the ferromagnetic state for the specimen with x=0.12 in a magnetic field of 14.6 T is reduced about 50% compared with that of the paramagnetic state in zero field. This means that the metamagnetic transition results in a drastic reduction of the spin fluctuation in the compound.