Four-state standard Potts model

We investigated magnetic and thermal properties of a one-dimensional 4-state Potts model by the method of Kramers-Wannier transfer-matrix. Not only magnetic field but also the interactions between nearest J and second J′ neighbors were taken into account. It was shown that in the case of a single crystal, this magnet could have up to four frustration fields at which magnetization has jumps and entropy tends to non-zero values at T→0. We found the exact analytical expressions for these frustration fields. When an external field crosses over the frustration fields cardinal changes of magnetic structures take place.