First and second order transition of frustrated Heisenberg spin systems |
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Authors: | D Loison KD Schotte |
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Institution: | Institut für Theoretische Physik,Freie Universit?t Berlin, Arnimallee 14, 14195, Berlin, Germany
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Abstract: | Starting from the hypothesis of a second order transition we have studied modifications of the original Heisenberg antiferromagnet
on a stacked triangular lattice (STA-model) by the Monte Carlo technique. The change is a local constraint restricting the
spins at the corners of selected triangles to add up to zero without stopping them from moving freely (STAR-model). We have
studied also the closely related dihedral and trihedral models which can be classified as Stiefel models. We have found indications
of a first order transition for all three modified models instead of a universal critical behavior. This is in accordance
with the renormalization group investigations but disagrees with the Monte Carlo simulations of the original STA-model favoring
a new universality class. For the corresponding x-y antiferromagnet studied before, the second order nature of the transition could also not be confirmed.
Received 17 May 1999 and Received in final form 30 July 1999 |
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Keywords: | PACS 05 70 Fh Phase transitions: general studies - 64 60 Cn Order disorder transformations statistical mechanics of model systems - 75 10 -b General theory and models of magnetic ordering |
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