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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. Physical Review, 65.

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Abstract

The effect of Zn2+ ion impurities on the phase transition temperature of single crystals of calcium cadmium acetate hexahydrate (CCDAH) has been studied using the electron-paramagnetic-resonance technique. The lowering of the phase transition temperature as a function 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-Cd(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 phase 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 > QH Natural history > QH301 Biology
Divisions: Faculty of Medicine, Health and Life Sciences > School of Biological Sciences
Depositing User: Mrs Patricia Nwokealisi
Date Deposited: 24 Apr 2015 20:08
Last Modified: 24 Apr 2015 20:08
URI: http://eprints.covenantuniversity.edu.ng/id/eprint/5118

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