STUDY OF THE VALENCE TRANSITION IN YBINCU4 BY INELASTIC NEUTRON-SCATTERING

In YbInCu4 a valence transition occurs from an almost stable trivalent phase for T>45K to an intermediate-valence state below 45K. We have investigated the imaginary part of the dynamic susceptibility X″ of YbInCu4 above and below the transition and compared it with spectra of the stable valent compound YbInNi4. YbInNi4 and YbInCu4 in the trivalent phase exhibit crystal-field (CF) excitations, centered at about 4meV. Below the valence transition in YbInCu4 the CF excitations disappear and instead we observe a broad magnetic signal centered at about 40meV, i.e., energy transfers ten times larger than the position of the CF lines of the stable valent phase. © 1990.