Magnetic properties in an alternating-spin ferromagnetic Ising chain

Using the transfer matrix technique, we investigated the magnetic properties of a ferromagnetic Ising chain with alternating-spins (S  , S′S′) and single-ion anisotropy. We have calculated some physical quantities of interest such as the z component of the total magnetization per particle (m  ) and magnetic susceptibility. In the regime of low temperatures, we observed the existence of magnetization plateaus. We constructed the phase diagrams of the magnetization in terms of the magnetic field and of the single-ion anisotropy for the case 12≤(S,S′)≤92. We were able to find a general rule for the magnetic transitions. We observed that the saturation value of the magnetization is msat=(S+S′)/2msat=(S+S′)/2.

Research highlights
► Ising chains with alternating-spins (S,S′)(S,S′) are solved without any approximation.
► Through the exact partition function we found the magnetization of the system.
► Plateaus were found in the magnetization curves, as observed in several experiments.
► The phase diagram for the magnetization of the system is generalized.