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Investigations on the spin-glass state in $Dy_{0.5}Sr_{0.5}MnO_$3 single crystals through structural, magnetic and thermal properties

Harikrishnan, S and Kumar, Naveen CM and Bhat, HL and Elizabeth, Suja and Roßler, UK and Dorr, K and Roßler, S and Wirth, S (2008) Investigations on the spin-glass state in $Dy_{0.5}Sr_{0.5}MnO_$3 single crystals through structural, magnetic and thermal properties. In: Journal of Physics: Condensed Matter, 20 (27). pp. 275234-1.

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Single crystals of $Dy_{0.5}Sr_{0.5}MnO_3$ are grown using the optical floating zone technique, and their structural, magnetic, transport and thermal properties have been investigated. Magnetization measurements under field-cooled and zero-field-cooled conditions display irreversibility below 35 K. The magnetization does not saturate up to fields of 5 T in the temperature range 5–350 K. AC susceptibility shows a cusp around 32 K that shifts to higher temperature with increasing frequency. This frequency dependence of the peak temperature follows a critical slowing down with exponent $zv$ = 3.6. Electrical resistivity shows insulating behavior, and the application of magnetic fields up to 10 T does not change this qualitative behavior. However, a marked negative magnetoresistance is observed in the paramagnetic phase reaching 80% at 70 K and 10 T. The observed resistivity behavior does not obey an activated type of conduction. These features are characteristic of spin-glass behavior in this half-doped insulating manganite. It is argued that the spin-glass-like state originates from the A-site disorder, which in turn results from the random distribution of cations with different ionic radii. Specific-heat measurements reveal a sizable linear contribution at low temperature that may be associated with the glassy magnetic ordering and a Schottky-like anomaly in a wide temperature range between 8 and 40 K. The istribution of Schottky levels is explained by the inhomogeneity of the molecular field in the spin-glass state that leads to variable splitting of the Kramers ground-state doublets in $Dy^{3+}$.

Item Type: Journal Article
Publication: Journal of Physics: Condensed Matter
Publisher: Institute of Physics
Additional Information: Copyright of this article belongs to Institute of Physics.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 21 Jul 2008
Last Modified: 19 Sep 2010 04:47
URI: http://eprints.iisc.ac.in/id/eprint/15182

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