GIANT MAGNETORESISTANCE AND THE MAGNETIC PHASE-TRANSITION IN TBNISN

Extraordinary large changes are found in the magnetoresistance of TbNi Sn single crystals at liquid helium temperatures. The large resistance changes correspond well to the magnetic phase transitions observed in multi-step magnetization processes. Such a magnetoresistance behavior of TbNiSn is explained well by the use of the semi-empirical equation s based on the Boltzmann transport theory. The results of the analysis require that the magnetoresistance in the phase below 2.1 K is determ ined by the ground state electrons which form a ''magnetic lattice'', while the other electrons in the excited state determine the phase abo ve 2.1 K.