Magnetism in doped Kondo insulators

Abstract

We consider the effect of substitution of small amounts of non-magnetic La for Ce in Kondo insulators of the CeNiSn type. In stoichiometric Kondo insulators, it appears that a gap on the scale of the Kondo temperature T_K, is opened in the excitation spectrum. Doping with small amounts of La introduces a dilute heavy-hole gas in which we argue that the hole-hole exchange coupling can lead to an antiferromagnetic ground state at relatively low doping levels. For higher doping levels the system becomes a dirty metal and, depending on the value of the effective conduction-electron-f-electron magnetic coupling J_K, may revert to a nonmagnetic state. Thus we anticipate the possibility of a ‘tongue’ of antiferromagnetic phase protruding into the non-magnetic region of the phase diagram at low to intermediate doping levels.