title: Universal temperature dependence of the magnetization of gapped spin chains.
abstract: A Haldane chain under applied field is analyzed numerically, and a clear minimum of magnetization is observed as a function of temperature. We elucidate its origin using the effective theory near the critical field and propose a simple method to estimate the gap from the magnetization at finite temperatures. We also demonstrate that there exists a relation between the temperature dependence of the magnetization and the field dependence of the spin-wave velocity. Our arguments are universal for general axially symmetric one-dimensional spin systems.
authors.affiliation: Department of Physics and Astronomy, The University of British Columbia, Vancouver, British Columbia, V6T 1Z1 Canada.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Maeda
authors.forename: Chisa
authors.initials: C
authors.lastname: Hotta
authors.forename: Masaki
authors.initials: M
authors.lastname: Oshikawa