Suppression of antiferromagnetic correlations by quenched dipole-type impurities

Citation
V. Cherepanov et al., Suppression of antiferromagnetic correlations by quenched dipole-type impurities, EUR PHY J B, 8(4), 1999, pp. 511-523
Citations number
38
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
EUROPEAN PHYSICAL JOURNAL B
ISSN journal
14346028 → ACNP
Volume
8
Issue
4
Year of publication
1999
Pages
511 - 523
Database
ISI
SICI code
1434-6028(199904)8:4<511:SOACBQ>2.0.ZU;2-3
Abstract
The effects of quenched dipole moments on a two-dimensional Heisenberg anti ferromagnet are found exactly, by applying the renormalization group to the appropriate classical non-linear sigma model. Such dipole moments represen t random fields with power law correlations. At low temperatures, they also represent the long range effects of quenched random strong ferromagnetic b onds on the antiferromagnetic correlation length, xi(2D), of a two-dimensio nal Heisenberg antiferromagnet. It is found that the antiferromagnetic long range order is destroyed for any non-zero concentration, x, of the dipolar defects, even at zero temperature. Below a line T proportional to x, where T is the temperature, xi(2D) is independent of T, and decreases exponentia lly with x. At higher temperatures, it decays exponentially with rho(s)(eff )/T, with an effective stiffness constant rho(s)(eff), which decreases with increasing x/T. The latter behavior is the same as for annealed dipole mom ents, and we use our quenched results to interpolate between the two types of averaging for the problem of ferromagnetic bonds in an antiferromagnet. The results are used to estimate the three-dimensional Neel temperature of a lamellar system with weakly coupled planes, which decays linearly with a: at small concentrations, and drops precipitously at a critical concentrati on. These predictions are shown to reproduce successfully several of the pr ominent features of experiments on slightly doped copper oxides.