Internal oscillations of kink-type solitons in one-dimensional antiferromagnets like TMMC

Abstract

The problem of internal oscillations of kink-type solitons in a one-dimensional easy-plane antiferromagnet is studied by analytical methods. Apart from the Goldstone mode a second local mode which is due to the coupling between in-plane and out-of-plane spin components has been derived. For typical experimental conditions in a model system like (TMMC) the frequency of this mode is very close to the bottom of the magnon band. Considering both a twofold and a weak sixfold in-plane crystal field anisotropy we found that close to the spin-flop transition the separation of this local mode from the magnon band is increased and dramatically affected by the sixfold anisotropy. We show that quantum properties of this mode are not important.

Truncated forms of the second-rank orthorhombic Hamiltonians used in magnetism and electron magnetic resonance (EMR) studies are invalid—Why it went unnoticed for so long?

“…(10) correspond to the case (a) D x 0. The values K/k B ffi0.3 K and K 2 /k B ffi4 mK at T ¼ 4.2 K cited in [53] yield the ratio K/K 2 ¼ 75, i.e. close to D z /D x E70 in [45].…”

“…close to D z /D x E70 in [45]. The discrepancies in the form of ZFS terms and the respective values of the crucial ratio of the axial to 'rhombic' ZFS parameter in [45,51,53] reinforce doubts concerning reliability of the model calculations based on truncated ZFS terms discussed above. Some comments on the term H 6 in Eq.…”

“…(10) are pertinent. It represents [53] 'a very weak hexagonal anisotropy' and was later given as S 2 K 6 sin 2 3j, i.e. 'the sixfold anisotropy reflecting the hexagonal symmetry of the crystal lattice'.…”

“…It should be pointed out that having provided no explicit form of Hamiltonian H 6 , the microscopic origin of this term is not justified and hence its physical mechanism is not clear. However, on the basis of symmetry arguments it seems that no appropriate ZFS terms exist for Mn 2+ in TMMC that would lead to the corresponding single-ion anisotropy term given in [53].…”