Year: 2002
Type: article
Abstract: The magnetic compound ${\mathrm{Ba}}_{2}{\mathrm{CuGe}}_{2}{\mathrm{O}}_{7}$ has recently been shown to be an essentially two-dimensional spiral antiferromagnet that exhibits an incommensurate-to-commensurate phase transition when a magnetic field applied along the c axis exceeds a certain critical value ${H}_{c}.$ The $T=0$ dynamics is described here in terms of a continuum field theory in the form of a nonlinear \ensuremath{\sigma} model. We are thus in a position to carry out a complete calculation of the low-energy magnon spectrum for any strength of the applied field throughout the phase transition. In particular, our spin-wave analysis reveals field-induced instabilities at two distinct critical fields ${H}_{1}$ and ${H}_{2}$ such that ${H}_{1}<{H}_{c}<{H}_{2}.$ Hence we predict the existence of an intermediate phase whose detailed nature is also studied to some extent.
Authors: J. Chovan, N. Papanicolaou, S. Komineas
Institutions: University of Crete, University of Bayreuth
Language: Latvian
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1964058545