B–T phase diagram of pure and doped YbInCu 4

Abstract

We have measured the high-field magnetization of Yb 1− x R x InCu 4 (R=Y, La, Ce) compounds up to 53 T in the temperature range 1.5–100 K using high-quality samples. The compounds undergo a sharp first-order valence transition from the intermediate-valent state to the trivalent state with increasing either temperature or magnetic field. Both the critical temperature and the magnetic field of the transition, T v and B v, increase by La or Ce substitution for Yb and decrease by Y substitution. We found that the relation between B v( T)/ B v(0) and T/ T v is given by [ B v( T)/ B v(0)] n +[ T/ T v] n =1 with 2.5⩽ n⩽3, which is inconsistent with the elliptic relation [ B v( T)/ B v(0)] 2+[ T/ T v] 2=1 reported previously. Possible reasons for the observed contradiction are discussed based on the percolation effect.