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X-Band ESR Determination of Dzyaloshinsky-Moriya Interaction in 2D SrCu$_2$(BO$_3$)$_2$ System

Andrej Zorko·Denis Arčon·Hans van Tol·Louis Claude Brunel·Hiroshi Kageyama
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Abstract

X-band ESR measurements on a single crystal of SrCu$_2$(BO$_3$)$_2$ system in a temperature range between 10 K and 580 K are presented. The temperature and angular dependence of unusually broad ESR spectra can be explained by the inclusion of antisymmetric Dzyaloshinsky-Moriya (DM) interaction, which yields by far the largest contribution to the linewidth. However, the well-accepted picture of only out-of-plane interdimer DM vectors is not sufficient for explanation of the observed angular dependence. In order to account for the experimental linewidth anisotropy we had to include sizable in-plane components of interdimer as well as intradimer DM interaction in addition to the out-of-plane interdimer one. The nearest-neighbor DM vectors lie perpendicular to crystal anisotropy c-axis due to crystal symmetry. We also emphasize that above the structural phase transition occurring at 395 K dynamical mechanism should be present allowing for instantaneous DM interactions. Moreover, the linewidth at an arbitrary temperature can be divided into two contributions; namely, the first part arising from spin dynamics governed by the spin Hamiltonian of the system and the second part due to significant spin-phonon coupling. The nature of the latter mechanism is attributed to phonon-modulation of the antisymmetric interaction, which is responsible for the observed linear increase of the linewidth at high temperatures.

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Andrej Zorko, Denis Arčon, Hans van Tol, Louis Claude Brunel, Hiroshi Kageyama. 2003-11-04. X-Band ESR Determination of Dzyaloshinsky-Moriya Interaction in 2D SrCu$_2$(BO$_3$)$_2$ System. https://doi.org/10.1103/physrevb.69.174420

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