Evidence of field-induced non-Fermi-liquid behavior in YbCu 5− xAl x compounds

Abstract

We measured the specific heat, magnetic susceptibility and electrical resistivity of YbCu 5− x Al x in magnetic fields up to 13 T. Between x=1.6 and 2 these compounds order antiferromagnetically with a Néel-temperature between 0.25 and 2 K, respectively. In high fields the antiferromagnetic transition is suppressed and a crossover to Fermi-liquid behavior occurs. At a critical field B cr, non-Fermi-liquid (nFl) behavior is found which is characterized by a −log T contribution to the specific heat C/ T down to 300 mK as well as deviations from T 2 behavior in the electrical resistivity. The magnetic susceptibility measured in B cr is proportional to 1− a√ T below 6 K. A scaling analysis of the specific heat and magnetization data obtained in higher fields ( B> B cr) points to collective effects responsible for the field-induced nFl behavior. This is the first system besides CeCu 6− x Ag x where field-induced nFl behavior is found.