Resonant quantum coherence of magnetization at excited states in nanospin system

2019-11-09 03:18:47

magnetic state quantum periodic states

责任者: Zhu Jia-Lin;Lu Rong;Kou Su-Peng;Hu Hui;Gu Bing-Lin 单位: Center for Adv. Study, Tsinghua Univ., Beijing, China 来源出处: European Physical Journal B(Eur. Phys. J. B (France)),2000/08/,16(3):507-13 摘要: The quantum interference effects induced by the Wess-Zumino term, or Berry phase are studied theoretically in resonant quantum coherence of the magnetization vector between degenerate states in nanometer-scale single-domain ferromagnets in the absence of an external magnetic field. We consider the magnetocrystalline anisotropy with trigonal, tetragonal and hexagonal crystal symmetry, respectively. By applying the periodic instanton method in the spin-coherent-state path integral, we evaluate the low-lying tunnel splittings between degenerate excited states of neighboring wells. And the low-lying energy level spectrum of mth excited state are obtained with the help of the Bloch theorem in one-dimensional periodic potential. The energy level spectrum and the thermodynamic properties of magnetic tunneling states are found to depend significantly on the total spins of ferromagnets at sufficiently low temperatures. Possible relevance to experiments is also discussed 关键词: ferromagnetism;magnetic anisotropy;magnetisation;specific heat;spin systems;resonant quantum coherence;magnetization;magnetic tunneling states;nanospin systems;crystal symmetry effect;Wess-Zumino term;Berry phase;degenerate states;single-domain ferromagnets;magnetocrystalline anisotropy;periodic instanton method;spin-coherent-state path integral;tunnel splittings;excited state;Bloch theorem;1D periodic potential;energy level spectrum;specific heat