Pressure-induced magnetic phase transitions in Yb Kondo lattice systems

In this paper we give a brief overview of the effect of pressure on the magnetic and electronic properties of Yb Kondo lattices using the Yb-170 Mossbauer technique, electrical resistance and X-ray diffraction. The selected materials were either nonmagnetic (YbCu2Si2 and Yb2Ni2Al) or ferromagnetic (YbNiSn). We show that pressure induces a first order transition to a magnetic ground state in both YbCu2Si2 and Yb2Ni2Al. In the former compound, the transition is accompanied by a valence change towards Yb3+ state. The behavior of both YbCu2Si2 and Yb2Ni2Al can be understood as resulting from a pressure enhancement of the RKKY interaction which finally dominates the Kondo effect. We demonstrate that the ground state properties of YbNiSn are governed by a volume dependent competition between anisotropic exchange interactions and crystal field anisotropy rather than by a direct competition between Kondo and RKKY interactions.