Topological phase interference effects in resonant quantum tunneling of the Neel vector between nonequivalent magnetic wells in mesoscopic single-domain antiferromagnets

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Title: Topological phase interference effects in resonant quantum tunneling of the Neel vector between nonequivalent magnetic wells in mesoscopic single-domain antiferromagnets
Author(s): Lu, Rong; Hu, Hui; Zhu, Jia-Lin; Wang, Xiao-Bing; Chang, Lee; Gu, Bing-Lin
Abstract: Resonant quantum tunneling of the Néel vector between nonequivalent magnetic wells is investigated theoretically for a nanometer-scale single-domain antiferromagnet with biaxial crystal symmetry in the presence of an external magnetic field applied along the easy anisotropy axis, based on the two-sublattice model. Both the Wentzel-Kramers-Brillouin exponent and the preexponential factors are evaluated in the instanton contribution to the tunneling rate for finite and zero magnetic fields by applying the instanton technique in the spin-coherent-state path-integral representation, respectively. The quantum interference or spin-parity effects induced by the topological phase term in the Euclidean action are discussed in the rate of quantum tunneling of the Néel vector. In the absence of an external applied magnetic field, the effect of destructive phase interference or topological quenching on resonant quantum tunneling of the Néel vector is evident for the half-integer excess spin antiferromagnetic nanoparticle. In the weak field limit, the tunneling rates are found to oscillate with the external applied magnetic field for both integer and half-integer excess spins. We discuss the experimental condition on the applied magnetic field which may allow one to observe the topological quenching effect for nanometer-scale single-domain antiferromagnets with half-integer excess spins. Tunneling behavior in resonant quantum tunneling of the magnetization vector between nonequivalent magnetic wells is also studied for a nanometer-scale single-domain ferromagnet by applying the similar technique, but in the large noncompensation limit.
Publication type: Journal article
Source: European Physical Journal B: Condensed Matter and Complex Systems, Vol. 14, no. 2 (Aug 2000), pp. 349-361
Publication year: 2000
FOR Code(s): 01 Mathematical Sciences; 02 Physical Sciences
Keyword(s): Antiferromagnetics; Macroscopic quantum phenomena; Magnetic systems; Measurement theory
Publisher: EDP Sciences and Springer
ISSN: 1434-6028
Publisher URL: http://dx.doi.org/10.1007/s100510050139
Peer reviewed