Magnetic properties of modified diamond spin chain

Abstract

The work is devoted to the theoretical study of the energy spectrum and magnetic properties of the modified antiferromagnetic spin (1/2, s) diamond chain. This is a frustrated mixed spin system with the unit cells formed by two spin ½ and one spin s>1/2. On the base of extended Lieb theorem we proved the possibility of the appearance of quantum phase transitions mediated by ratio of coupling parameters at arbitrary nonzero value of the spin s for the above model. The results of our exact diagonalization study for some finite chain clusters with s=1 supports this conclusion. We also studied analytically and numerically magnetic properties of Heisenberg –Ising diamond mixed spin chain. The exact energy spectrum of this model is found in analytical form at arbitrary values of model parameters. On the base of this spectrum we studied the field dependence of two-particle correlators for neighbor Ising spins. It was found that at special relation between coupling parameters there is a critical value of external magnetic field for which the above correlator takes zero value (the absence of the correlation between Ising spins). For infinite spin chain model we studied field dependence of specific magnetization by means of classical transfer- matrix method and found intermediate plateau in the low-temperature magnetization profile. According to our calculations, the size of this plateau depends strongly on the relations between coupling parameters of the model. We hope this feature of our model gives new possibilities for the design of new magnetic chemo-sensors.