Deceptive signals of phase transitions in small magnetic clusters

Heinrich Stamerjohanns   Phone: +49-(0)441-798-4276   Fax: +49-(0)441-798-3201
Oliver Muelken   Phone: +49-(0)441-798-3362   Fax: +49-(0)441-798-3201
Peter Borrmann   Phone: +49-(0)441-798-3362   Fax: +49-(0)441-798-3201

Small systems group   University of Oldenburg, Germany


Date: 20010709

Article: published in Phys. Rev. Lett. 88, 053401 (2002)

phase transition, finite systems, canonical ensemble, zeros, complex temperature, magnetic clusters, negative temperature

We present an analysis of the thermodynamic properties of small
transition metal clusters and show how the commonly used indicators of
phase transitions like peaks in the specific heat or magnetic
susceptibility might lead to deceptive interpretations of the
underlying physics. The analysis of the distribution of zeros of the
canonical partition function in the whole complex temperature plane
clearly reveals the nature of the transition. Specifically we show
that signals in the magnetic susceptibility at positive temperatures
have their origin at zeros lying at negative temperatures.

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