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EPR studies of the effect of Zn2+ ion impurities in phase transition of CaCd(CH3C00)4·6H20 crystals

De, Dilip Kumar (2002) EPR studies of the effect of Zn2+ ion impurities in phase transition of CaCd(CH3C00)4·6H20 crystals. PHYSICALREVIEWB, 65.

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1be effect of Zn2 + ion impurities on tbe phase transition temperature of single crystals of calcium cadmium acetate hexahydrate (CCDAH) ha~ been studied using the electron-paramagnetic-resonance technique. The lowering of the pha~ transition temperature as a fimction of increasing Zn2+ impurity ion concentration in the crystals has been observed to be quite different from that found in our earlier studies of Cu2+ and Mn2+ ion doped crystals. Though the observed lowering of phase transition temperature with atomic fraction x of the Zn2 + impurity ion can be explained fairly well in terms of mean-field theory and a soft mode arising out of the harmonic vibration of the Ca-C~l-x)Znx-Ca chain along the c axis of the crystal, contrary to expectation, values of constants (such as the ratio of the square of the soft-mode frequency before transition, the mean-field constant. and the phase transition temperature, etc. of the pure crystal) are quite different from that obtained by fitting the phase transition temperatures in the Cu2+ ion only impurity doped crystals. The temperature variation of the spin-Hamiltonian parameters of the Cu2+ ion probe in the Zn2+ -doped crystal of CCDAH is somewhat different from that in the Cu2+ ion only doped crystal. Deviation from mean-field theory is then considered in the Zn2+ impurity driven modification of phase transition of the crystal and good agreement between the observed and computed values of pbase transition temperature as a function of the Zn2 + atomic fraction has been obtained using the same values of the said constants as obtained for Cu2+ ion only impurity doped crystals.

Item Type: Article
Subjects: Q Science > Q Science (General)
Q Science > QC Physics
Divisions: Faculty of Engineering, Science and Mathematics > School of Physics
Depositing User: Mrs Hannah Akinwumi
Date Deposited: 12 Apr 2015 20:58
Last Modified: 07 Sep 2015 15:12

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