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Studies of the Local Phase-transition Behaviour for Ni

+

-II Centers in RbCaF

3

Crystal from EPR Data

Wen-Chen Zhenga, b, cand Shao-Yi Wua, b

aDepartment of Material Science, Sichuan University, Chengdu 610064, P. R. China

bInternational Center for Materials Physics, Chinese Academy of Sciences, Shenyang 110015, P. R. China

cKey Laboratory of Radiation Physics and Technology, Ministry of Education of China, Sichuan University, Chengdu 610064, P. R. China

Reprint requests to W.-C. Z.; E-mail: zhengwenchen@netease.com Z. Naturforsch. 55a, 915 – 917 (2000); received September 12, 2000

By fitting the calculated EPR gi(i = x, y, z) factors to the observed values, the local release factor kl which is introduced to characterize the release (or elongation) effect of impurity-ligand bonds along the rotational axis in the cubic-to-tetragonal phase transition of ABX3perovskites, is obtained for the Ni+- II center in RbCaF3crystal. The result shows that, similar to the local rotational angle (or order param- eter) G, the local release factor is unlike that of the host crystal. It suggests that in the doped crystal the impurity can affect the local phase transition behaviour in the vicinity of impurity ions.

Key words: Local Phase Transition Behaviour; E. P. R.; Crystal-field Theory; Ni+ion; RbCaF3. PACS: 64.70Kb; 76.30Fc; 71.70Ch

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