Low-Dimensional Quantum Spin Systems in Pulsed Magnetic Fields up to 50 T

Abstract

Low-dimensional spin systems reveal new and unexpected physical phenomena such as distinct plateaus in the magnetization as a function of magnetic field. In this paper, we present ESR and ultrasonic measurements for the quasi-two-dimensional spin system SrCu 2 (BO 3 ) 2 and the spinchain compound NH 4 CuCl 3 in magnetic fields up to 50 T. From the combination of our experimental techniques we obtain detailed information about the spin state, the magnetic excitations and their interaction with phonons. The dimerized quantum-spin system SrCu 2 (BO 3 ) 2 exhibits plateaus in the magnetization and shows surprisingly strong magneto-elastic effects as a function of temperature and magnetic field. The pronounced elastic anomalies indicate a resonant interaction between the sound wave and the magnetic excitations. In contrast to SrCu 2 (BO 3 ) 2 we find in NH 4 CuCl 3 a linear relation of the c 66 mode and the magnetic susceptibility.