TY - JOUR

T1 - Suppression of antiferromagnetic correlations by quenched dipole-type impurities

AU - Cherepanov, V.

AU - Korenblit, I. Ya

AU - Aharony, A.

AU - Entin-Wohlman, O.

PY - 1999/4/11

Y1 - 1999/4/11

N2 - The effects of quenched dipole moments on a two-dimensional Heisenberg antiferromagnet are found exactly, by applying the renormalization group to the appropriate classical non-linear sigma model. Such dipole moments represent random fields with power law correlations. At low temperatures, they also represent the long range effects of quenched random strong ferromagnetic bonds on the antiferromagnetic correlation length, ξ2D, of a two-dimensional 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 ∞ x, where T is the temperature, ξ2D is independent of T, and decreases exponentially with x. At higher temperatures, it decays exponentially with ρeffs/T, with an effective stiffness constant ρeffs, which decreases with increasing x/T. The latter behavior is the same as for annealed dipole moments, 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 Néel temperature of a lamellar system with weakly coupled planes, which decays linearly with x at small concentrations, and drops precipitously at a critical concentration. These predictions are shown to reproduce successfully several of the prominent features of experiments on slightly doped copper oxides.

AB - The effects of quenched dipole moments on a two-dimensional Heisenberg antiferromagnet are found exactly, by applying the renormalization group to the appropriate classical non-linear sigma model. Such dipole moments represent random fields with power law correlations. At low temperatures, they also represent the long range effects of quenched random strong ferromagnetic bonds on the antiferromagnetic correlation length, ξ2D, of a two-dimensional 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 ∞ x, where T is the temperature, ξ2D is independent of T, and decreases exponentially with x. At higher temperatures, it decays exponentially with ρeffs/T, with an effective stiffness constant ρeffs, which decreases with increasing x/T. The latter behavior is the same as for annealed dipole moments, 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 Néel temperature of a lamellar system with weakly coupled planes, which decays linearly with x at small concentrations, and drops precipitously at a critical concentration. These predictions are shown to reproduce successfully several of the prominent features of experiments on slightly doped copper oxides.

KW - 75.10.-b General theory and models of magnetic ordering

KW - 75.10.Nr Spin-glass and other random models

KW - 75.50.Ee Antiferromagnetics

UR - http://www.scopus.com/inward/record.url?scp=0000619272&partnerID=8YFLogxK

U2 - 10.1007/s100510050719

DO - 10.1007/s100510050719

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AN - SCOPUS:0000619272

SN - 1434-6028

VL - 8

SP - 511

EP - 523

JO - European Physical Journal B

JF - European Physical Journal B

IS - 4

ER -