The study of the phase diagram and internal energy of the mixed spin-3/2 and spin-5/2 ferrimagnetic Ising system with interlayer coupling by effective-field theory; a simple approach of calculating internal energy

Phase diagrams and internal energies of a layered Ising system were studied using the effective-field theory (EFT) with correlations. The results show that the critical temperature becomes larger, while the compensation temperature and the internal energy become smaller with the increase in the interlayer. coupling and the crystal-field. The traditional method to calculate the internal energy of the Ising system by the EFT is based on a differential of its differential operator identity. So an additional differential procedure must be carried out when calculating the internal energy. In this paper, a new function on which the differential operator acts is introduced to solve this problem, without performing the additional differential procedure. The results obtained by the two methods are exactly the same.