Research Papers in Physics and Astronomy


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Published in Journal of Physics: Condensed Matter 13 (2001), pp. L811–L817. Copyright © 2001 Institute of Physics Publishing Ltd. Used by permission. Online at


The isothermal magnetization m (H) of the metamagnet FeCl2 is measured in axial magnetic fields 0 ≤ μ0Ha ≤ 12 T at temperatures 34 ≤ T ≤ 53 K above the Néel temperature, where the system is essentially a two-dimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent μ of the Yang-Lee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the Lee-Yang unit circle in the complex plane. In accordance with the hypothesis of universality, a critical exponent close to the theoretical prediction for the two-dimensional Ising ferromagnet, μ = –1/6, is found.

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