Eur. Phys. J. B 4, 223-231 (1998)
https://doi.org/10.1007/s100510050373

Magnetic quantum coherence in trigonal and hexagonal systems

¹ CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, P.R. China
² Department of Physics, Tsinghua University, Beijing 100084, P.R. China
³ Center for Advanced Study, Tsinghua University, Beijing 100084, P.R. China
⁴ Department of Physics, Guangzhou Normal College, Guangzhou 510400, P.R. China and Institute of Physics, Academia Sinica, P.O. Box 603-99, Beijing 100080, P.R. China

Corresponding author: ^a rlu@Phys.Tsinghua.edu.cn

Received: 18 November 1997
Revised: 18 March 1998
Accepted: 6 April 1998
Published online: 15 July 1998

Abstract

The tunneling behaviors of the magnetization vector are studied in ferromagnetic systems with trigonal and hexagonal crystal symmetries, respectively. The Euclidean transition amplitudes between the energetically degenerate easy directions are evaluated with the help of the dilute instanton-gas approximation. By using the effective Hamiltonian method, the ground-state tunneling level splittings are clearly shown for each kind of symmetry and are found to depend on the parity of the total spin of the ferromagnetic particle. The effective Hamiltonian method is demonstrated to be equivalent to the dilute instanton-gas approximation. Possible relevance to experiments is discussed.