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Study of Quantum Phenomena in a One-Dimensional Magnetic System

一维磁系统中的量子现象研究

基本信息

批准号：
03452047
负责人：
KATSUMATA Koichi
金额：
$ 4.48万
依托单位：
The Institute of Physical and Chemical Research(RIKEN)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03452047/
关键词：
One-dimensional magnetic system Quantum spin system Haldane gap VBS ground state NENP ESR

项目摘要

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.

本项目的目的是阐明一维磁系统中的量子现象。（1）用电子自旋共振（ESR）方法测量了典型的自旋（S）单线链Heisenberg反铁磁体NENP掺杂少量Cu后的电子自旋共振（ESR）谱。在ESR谱中得到了两组超精细结构。考虑到Cu原子核和电子自旋之间的超精细相互作用，并与Cu原子附近Ni原子的分数自旋自由度耦合，很好地解释了这一结果.（2）对含3.3at.%的NENP单晶进行了稳态磁场下8 T和脉冲磁场下40 T的磁化强度测量Cu.磁化强度在低磁场下迅速增加，并在4 T以上达到饱和。当磁场进一步增加时，磁化强度再次开始增加。基于三个S=1/2自旋模型，定量地解释了低场区磁化强度的场依赖性。（3）在脉冲强磁场中对S=1的一维海森堡反铁磁体TMNIN和NINAZ进行了磁化强度测量。磁化强度在低场区非常小，并在临界场以上开始急剧增加。这种磁化行为与Katsumata等人在NENP中观察到的磁化行为相似。因此，实验证实了TMNIN和NINAZ中存在Haldrons间隙。（4）通过对快速生长的NENP单晶的ESR和磁化强度测量，我们观察到了分数自旋自由度。