| Abstract |
According to Haldane's predictions, the one dimensional quantum antiferromagnets of integer spin, have a magnetic disordered ground state, which is separated from the first excited state by an energy gap. We have studied a quasi-one-dimensional system, PbNi2V2O8, which has spin value 1. The analysis has been focused on the impact of substituting the magnetic ions of Ni by the non-magnetic Mg ions on the magnetism of the system. The pristine sample PbNi2V2O8 was prepared by the Sol-Gel method, while the dopants PbNi2-xMgxV2O8 , depending on the value of x, were prepared by the Solid State Reaction. The x-ray measurements on powder samples indicated that the material resides on the I41cd space group. Moreover, the samples' impurities are less then 4%. The analysis of the magnetic susceptibility measurements of the pristine sample suggested that the energy gap is approximately 34K and that the exchange integral J is 91K. The method of elastic neutron scattering has been used on powder samples in order to determine the magnetic structure of the dopants. The former procedure pointed out that the substitution of Ni ions by Mg ones induces long range antiferromagnetic order. This response is discussed and finally the model of E.Shender-S. Kivelson is adopted. The last conclusion of the above study points out the existence of a crucial value in the proportion of Mg doping at which the system reaches the maximum antiferromagnetic coupling. This result is clearly indicated by the magnetic susceptibility measurements on the PbNi2-xMgxV2O8 dopants.
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Επιβολή μαγνητικής τάξης σε μονοδιάστατα συστήματα. PbNi2-xMgxV2O8
