The European Physical Journal B - Condensed Matter and Complex Systems

, Volume 16, Issue 3, pp 507–513

Resonant quantum coherence of magnetization at excited states in nanospin systems with different crystal symmetries


  • Jia-Lin Zhu
    • Center for Advanced StudyTsinghua University
  • Rong Lü
    • Center for Advanced StudyTsinghua University
  • Su-Peng Kou
    • Center for Advanced StudyTsinghua University
  • Hui Hu
    • Department of PhysicsTsinghua University
  • Bing-Lin Gu
    • Center for Advanced StudyTsinghua University

DOI: 10.1007/s100510070210

Cite this article as:
Zhu, J., Lü, R., Kou, S. et al. Eur. Phys. J. B (2000) 16: 507. doi:10.1007/s100510070210


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.

PACS. 75.45.+j Macroscopic quantum phenomena in magnetic systems75.10.Jm Quantized spin models03.65.Bz Foundations, theory of measurement, miscellaneous theories (including Aharonov-Bohm effect, Bell inequalities, Berry's phase)
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© EDP Sciences, Springer-Verlag, Società Italiana di Fisica 2000