Study of Quantum Phenomena in a One-Dimensional Magnetic System

点击翻译按钮获取中文摘要

It is the aim of the present project to clarify the quantum phenomena in a one-dimensional magnetic system. The important findings obtained from this study are summarized below:(1)An electron spin resonance(ESR) measurement has been performed on a typical spin(S) one linear chain Heisenberg antiferromagnet NENP doped with a small amount of Cu. Two sets of hyperfine structure are obtained in the ESR spectrum. The result is well explained by taking into account the hyperfine interaction between the Cu nuclear and electron spins which couples with the fractional spin degrees of freedom induced at the Ni site neighboring the Cu atom.(2)Magnetization measurements up to 8T in a steady field and up to 40T in a pulsed field are made on a single crystal of NENP containing 3.3 at.% Cu. The magnetization increases rapidly at low fields and becomes saturated above 4T. The magnetization begins to increase again when the magnetic field is increased further. The field dependence of the magnetization at the low field region is quantitatively explained based on the three S=1/2 spins model.(3)Magnetization measurements on S=1 one-dimensional Heisenberg antiferromagnets TMNIN and NINAZ have been performed in a pulsed high magnetic field. The magnetizations are very small in the low field region and begin to increase sharply above the critical fields. This behavior of the magnetization is similar to that observed before in NENP by Katsumata et al. Thus, the existence of the Haldane gap in TMNIN and NINAZ is confirmed experimentally.(4)From an ESR and magnetization measurements on a rapidly grown single crystal of NENP, we have observed the fractional spin degrees of freedom.