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MA: Magnetismus
MA 19: Spinstrukturen und magnetische Phasenübergänge (incl. Sensoren(19.11) und Messmethoden(19.12-13))
MA 19.10: Talk
Thursday, March 14, 2002, 17:30–17:45, H23
Absence of Spontaneous Magnetic Order at Nonzero Temperature in One- and Two-Dimensional Heisenberg and XY Systems with Long-Range Interactions — •Patrick Bruno — Max-Planck-Institut für Mikrostruturphysik, Weinberg 2, O6120 Halle, Germany
The Mermin-Wagner theorem is strengthened so as to rule out
magnetic long-range order at T>0 in one- or two-dimensional
Heisenberg and XY systems with long-range interactions
decreasing as R−α with a sufficiently large exponent
α [1]. For oscillatory interactions, ferromagnetic long-range
order at T>0 is ruled out if α ≥ 1 (D = 1) or
α >5/2 (D = 2). For systems with monotonically decreasing
interactions, ferro- or antiferromagnetic long-range order at
T>0 is ruled out if α ≥ 2D.
[1] P. Bruno, Phys. Rev. Lett. 87, 137203 (2001).