#2001.06.16

J. Phys. A.: Math. Gen 32 (1999) 6687-6704

Unified spin-wave theory for quantum spin systems with single-ion anisotropies

Lei Zhou and Yoshiyuki Kawazoe

Abstract:

By introducing a new spin-Bose transformation which incorporates the single-site
spin-states miximg effect self-consistently, we establish a unified spin-wave
approach, applicalbe to an arbitrary spin-number case and general spin configurations,
for quantum spin systems with single-ion anisotropies. The conventional
Holstein-Primakoff (H) method completely fails for such systems with easy-plane
anisotropy and sometimes fails for those with easy axis anisotropy, while these
difficulties have been overcome successfully by the new method. In some limiting
cases, the present method recovers the result of old theories which are valid in such
cases. Applications to magnetic multilayers show that the new method is useful to
remove the unphysical instability predicted by the conventional HP mehtod.