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EPR studies of phase transitions in cadmium calcium acetate hexahydrate as a function of different paramagnetic impurity-ion concentrations

Oguama, F. A. and Shields, H. and De, Dilip Kumar (1997) EPR studies of phase transitions in cadmium calcium acetate hexahydrate as a function of different paramagnetic impurity-ion concentrations. PHYSlCAL REVIEW B, 56 (5).

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Abstract

The phase tt':lnsition in cadmium calcium acetate hexahydrate (CCDAH) has been studied in detail with electron paramagnetic resonance (J;PR) as a function of two different paramagnetic ion concentrations. namely. Cu:• and Mn:• ions. The change in transition temperature (1:!2-143 Kl with Cuz• ion concentrations is explained in terms of mean-field theory and a soft vibrational mode of the -Ca-Cd1 _ ,Cu,-Ca- chain along the c axis of the crystal. While the same theory can also explain our observed transition temperature ( 118-128 K) as a function of the Mn2• ion concentration in this crystal. it does not explain why the limiting value of the transition temperature (i.e .• 145 K) of CaCd1 -.,CuzCCH3C00)4 ·6H~O as x tends to zero, is strikingly different from the limiting value of ( -128..+ K) of CaCd1_.,Mn,(CH3C00)4·6H:O as x tends to zero. The same theory also successfully c:xplains the absence of any phase transition in isomorphous CaCu(CH 3C00)~·6H 20. The value of -dT~Id.t is significantly higher with Mn:• than with Cu!• in CCDAH. [50163-1829(97)01329-5]

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: 22 Apr 2015 14:48
Last Modified: 22 Apr 2015 14:48
URI: http://eprints.covenantuniversity.edu.ng/id/eprint/5087

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