FIELD-INDUCED DESTRUCTION OF HEAVY FERMION STATE IN URU2SI2

High-field magnetization and magnetoresistance of URu2Si2 single crystal are investigated up to 600 kOe. Three-step metamagnetic transitions are obtained with the transition fields of 358, 365 and 396 kOe at 1.3 K. The experimental results are explained quantitatively by introducing the model that the heavy Fermion state produced by the mixing of the f- and conduction electrons is destroyed by applying the field and that the exchange interactions between the recovered local f-electron magnetic moments on the uranium atom play an important role on the magnetic properties at high field. The frustration due to the exchange interactions induces the three-step metamagnetic transitions. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.