Yang-Lee edge singularities determined from experimental high-field magnetization data

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