Transition from Superparamagnetism to Ferromagnetic Single-Domain in a Heisenberg Model for Nano-cluster Magnetic System

• 来源期刊: 中国物理快报（英文版）
• 年，卷（期）: 2000,（5）
• 所属期刊栏目: Condensed matter
• 页码范围: 367-369
• 页数: 3页
• 语种: 英文

摘要

By considering a magnetic system of an ensemble of nanometer clusters without any external magnetic field, the Monte Carlo simulation of the Heisenberg model is used to investigate the transition from a superparamagnetism to a ferromagnetic single-domain state, which is caused by the growth of the clusters. We studied the variation of the dynamic growth exponent P and the transition critical size of the cluster Nc against the reduced temperature t and the uniaxial anisotropy constant A. We found that the growth exponent maximized at a certain temperature,other than being taken as a universal constant as some researchers suggested previously.