Zeros of the partition function for higher-spin 2D Ising models

We present calculations of the complex-temperature zeros of the partition functions for 2D Ising models on the square lattice with spin s=1, 3/2 and 2. These give an insight into complex-temperature phase diagrams of these models in the thermodynamic limit. Support is adduced for a conjecture that all divergences of the magnetization occur at endpoints of arcs of zeros protruding into the FM phase. We conjecture that there are 4(s²)-2 such arcs for s>or=1, where (x) denotes the integral part of x.