METAMAGNETISM AND LARGE MAGNETORESISTANCE IN TBNI2B2C

The antiferromagnetic non-superconducting compound TbNi2B2C crystalliz es in the same LuNi2B2C-type structure as the superconducting rare-ear th borocarbides. Below 15 K the magnetization curves of polycrystallin e TbNi2B2C show an upward curvature of the magnetization versus field curves, i.e. a metamagnetic behaviour. At low temperatures the field d ependence of resistivity rho is non-monotonic and the magnetoresistanc e ratio MR = [rho(H)-rho(0)]/rho(0) even changes its sign. Near T = T- N the value of MR is negative and its magnitude increases monotonicall y with increasing fields up to about 45% at the maximum available fiel d of 16 T. The magnetoresistance of this material is isotropic with re spect to the angle between current and field. The observed effects can be understood within a theoretical approach of the giant magnetoresis tance developed for artificial as well as natural layered structures, taking into account topological changes of the Fermi surface caused by metamagnetic transitions, together with field-reduced spin-disorder s cattering. (C) 1998 Elsevier Science B.V. All rights reserved.