Temperature-dependent electron paramagnetic resonance studies of charge-ordered Nd0.5Ca0.5MnO3

Joshi, Janhavi P and Gupta, Rajeev and Sood, AK and Bhat, SV and Raju, AR and Rao, CNR (2002) Temperature-dependent electron paramagnetic resonance studies of charge-ordered Nd0.5Ca0.5MnO3. In: Physical Review B, 65 . 024410/1-8.

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Abstract

We report electron paramagnetic resonance measurements on single crystalline and powder samples of Nd0.5Ca0.5MnO3 across the charge-ordering transition at Tco = 240 K down to the antiferromagnetic ordering transition at TN = 140 K. The changes in the linewidth, g-factor and intensity as functions of temperature are studied to understand the nature of spin-dynamics in the system. We explain the observed large decrease in the linewidth from TN to Tco in terms of motional narrowing caused by the hopping of the Jahn–Teller polarons yielding an activation energy of Ea = 0.1 eV. Similar analysis of data on Pr0.6Ca0.4MnO3 published earlier gives Ea = 0.2 eV. Below Tco, the g-value increases continuously suggesting a gradual strengthening of the orbital ordering. We give a qualitative explanation of the maximum in the asymmetry ratio A/B observed at Tco and its temperature dependence in single crystal spectra which also supports the model of motional narrowing. ©2001 The American Physical Society

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	Copyright for this article belongs to American Physical Society (APS).
Keywords:	neodymium compounds;calcium compounds;paramagnetic resonance;EPR line breadth;Jahn-Teller effect;polarons;spectral line narrowing;charge-ordered states;antiferromagnetic materials;magnetic transitions;g-factor;magnetic particles;spin dynamics
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	10 Dec 2004
Last Modified:	19 Sep 2010 04:14
URI:	http://eprints.iisc.ac.in/id/eprint/1193

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