Magnetic properties of generalized polyallyl spin chain
The work is devoted to the theoretical simulation of low-temperature magnetic properties of generalized polyallyl spin chain with the antiferromagnetic coupling of the neighboring spins (GPSC) - spin model of a family of quasi-one dimensional molecular ferrimagnets. First, the exact energy spectra of Heisenberg spin Hamiltonians of the finite lattice clusters of GPSC with the spins of the main chain s=1/2 and pendant spins š=1 have been studied by means of the exact diagonalization method. The calculations were performed for different positive values of the coupling parameters for neighboring spins of the main chain of GPSC clusters. On the base of the above exact energy spectra and the Boltzmann distribution law the field dependencies of magnetization of finite lattice clusters are calculated numerically at different temperatures. In the result, for low temperatures the presence of intermediate plateau in field dependencies of the cluster magnetization has been shown. These calculations demonstrated the stabilization of the intermediate magnetization plateau with the growth of the spin coupling along the main chain of GPSC clusters. In addition, the numerical study of temperature dependence of zero field magnetic susceptibility of 12- spin clusters of GPSC gives the results which are similar to the 1D model of molecular ferrimagnets like necklace spin ladder.
Similar calculations of the magnetization profile were performed for infinite Heisenberg –Ising GPSC model with Ising type of the antiferromagnetic interactions between the neighboring spins of the main chain. The classical transfer- matrix method was used for this purpose. In the result, it was shown the presence of an intermediate plateau in the low-temperature magnetization profile of infinite chain model and the increase of the plateau size with increasing of the Ising coupling between the spins of the main chain.
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