Title:	Charge ordering in the rare-earth manganates: the origin of the extraordinary sensitivity to the average radius of the A-site cations,<rA>.
Authors:	Arulraj, Anthony Santhosh, P.N. Srinivasa Gopalan, R. Guha, Ayan Raychaudhuri, A.K. Kumar, N. Rao, C.N.R.
Issue Date:	Sep-1998
Publisher:	IOP Publishing Ltd.
Citation:	Journal of Physics - Condensed Matter, 1998, Vol.10, p8497-8504
Abstract:	The charge ordering in , which occurs on cooling the ferromagnetic metallic ground state, is readily destroyed on application of a magnetic field of 6 T. For , for which the ground state is charge ordered, on the other hand, magnetic fields have no effect on the charge ordering. In order to understand such a marked difference in charge-ordering behaviour of the manganates, we have investigated the structure as well as the electrical and magnetic properties of compositions (Ln = Nd, Sm, Gd and Dy) wherein varies over the range 1.17-1.13 Å. The lattice distortion index, D, and charge-ordering transition temperature, , for the manganates increase with the decreasing . The charge-ordered state is transformed to a metallic state on applying a magnetic field of 6 T in the case of , but this is not the case with the analogous Sm, Gd and Dy manganates with less than 1.17 Å. In order to explain this behaviour, we have examined the -dependence of the Mn-O-Mn bond angle, the average Mn-O distance and the apparent one-electron bandwidth, obtained from these structural parameters. It is suggested that the extraordinary sensitivity of the charge ordering to arises from factors other than those based on the Mn-O-Mn bond angle and average Mn-O distances alone. It is possible that the competition between the covalent mixing of the oxygen orbital with the A-site and B-site cation orbitals plays a crucial role. Strain effects due to size mismatch between A-site cations could also cause considerable changes in .
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/2665
ISSN:	0953-8984 1361-648X (Online)
Alternative Location:	http://dx.doi.org/10.1088/0953-8984/10/38/010
Copyright:	1998 IOP Publishing Ltd.
Appears in Collections:	Research Papers (TP)

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