X-band ESR determination of Dzyaloshinsky-Moriya interaction in the two-dimensional SrCu2(BO3)2 system -: art. no. 174420

X-band ESR measurements on a single crystal of SrCu2(BO3)(2) system in a temperature range between 10 K and 580 K are presented. The temperature and angular dependence of rather broad ESR spectra can be explained by the inclusion of antisymmetric Dzyaloshinsky-Moriya (DM) interaction. However, the well-accepted picture of only out-of-plane interdimer DM vectors is not sufficient to explain the observed angular dependence. In order to account for the experimental linewidth anisotropy we additionally include sizable in-plane components of interdimer as well as intradimer DM interaction. We also emphasize that in addition to static buckling of crystal planes a recently introduced dynamical mechanism allowing for instantaneous DM interaction should be important and estimate the average size of intradimer DM vectors D-perpendicular to=3.6+/-0.5 K. 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.