Double-peak specific heat feature in frustrated antiferromagnetic clusters
A. V. Syromyatnikov, S. V. Maleyev
St.Petersburg Nuclear Physics Institute RAS, Gatchina, 188300, Russia
PACS: 75.10.Jm, 75.40.Cx, 75.50.Ee
Abstract
We study the nature of a double-peak specific heat structure in
kagome clusters. A cluster containing 12 spins is considered thoroughly by
means of numerical diagonalization. On base of analysis of exact spectra
simple models are proposed to explain the nature of the low-T peak at
Tl<Δ (Δ is the spin gap) in this case and in those of larger
clusters studied so far. Using these models we show that the rapid increase
in density of states just above the spin gap gives rise to the peak, and
clarify the weak magnetic field sensitivity of the peak. Spin susceptibility
and entropy are considered as well. Our approach could be appropriate for
other frustrated antiferromagnetic systems.