Magnetoelastic effects and magnetic anisotropy in the intermediate-valence compound YbInCu4

Abstract YbInCu 4 compound exhibits a first-order valence transition of Yb from a trivalent state to a mixed-valence state with decreasing temperature. Here we provide an overview of our recent high-field and high-pressure measurements of magnetization, thermal expansion and magnetostriction of the valence-fluctuating compound. The results are analyzed using the Kondo single-impurity model. It is shown that the change of the 4 f –conduction band electron hybridization is responsible for a large modification of the physical properties of YbInCu 4 at the valence transition. The volume magnetostriction is rather large for the low-temperature mixed-valence state, but strongly suppressed in the high-temperature local-moment state. From the magnetization measurements of the oriented YbInCu 4 single crystal, an appreciable anisotropy was found in the susceptibility, high-field magnetization, effective moment, paramagnetic Curie temperature and critical field of the valence transition. The type of the magnetic anisotropy and the value of anisotropic magnetoelastic coupling constant do not change significantly on going from the mixed-valence to the local-moment state. The anisotropic magnetostriction and magnetic anisotropy are described well in terms of a single-ion model of the interaction of anisotropic 4 f -shell of Yb ion with the crystal electric field.