| Popis: |
We present magnetostriction and thermal expansion measurements on the orthorhombic intermediate valence compound CeNi, at low temperature along the three symmetry axes. The field effects are clearly the sum of a main contribution arising from the intermediate valency character, which is temperature independent, and a smaller one whose temperature and field dependence is characteristic of Ce 3+ impurities. The low temperature thermal expansion and the main contribution to the magnetostriction are large and strongly anisotropic, the b -axis showing a particularly different behaviour. These results can be accounted for in a model based on an electronic free energy F e = − kTNf ( T / T f ), where the fluctuation temperature T f (ϵ a ,ϵ b ,ϵ c ) depends on the strains ϵ a ,ϵ b ,ϵ c in a different way. In this model the anisotropies of the thermal expansion and the magnetostriction are related to strong differences between the 3 Gruneisen parameters γ λ = − ∂ In T f /∂ϵ λ . Finally, we discuss the microscopic mechanisms wchic can give rise to this behaviour. |
