Ultrasonic anomaly near the charge ordering transition in Sr-doped Nd0.3La0.2Ca0.5−x Sr x MnO3 Manganites
Sr doping in the charge-ordered compound Nd0.3La0.2Ca0.5−x Sr x MnO3 has been systematically studied to examine its effect on ultrasonic velocity and elastic moduli as well as magnetic and electrical transport properties. DC electrical resistivity, ρ and AC susceptibility, χ′ measurements showed all...
| Main Authors: | , , , |
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| Format: | Article |
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Springer US
2014
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| Online Access: | http://www.dx.doi.org/10.1007/s10948-013-2389-8 http://www.dx.doi.org/10.1007/s10948-013-2389-8 |
| Summary: | Sr doping in the charge-ordered compound Nd0.3La0.2Ca0.5−x Sr x MnO3 has been systematically studied to examine its effect on ultrasonic velocity and elastic moduli as well as magnetic and electrical transport properties. DC electrical resistivity, ρ and AC susceptibility, χ′ measurements showed all samples exhibit metal-insulator (MI) behavior accompanied by ferromagnetic-paramagnetic (FM-PM) transition where the MI transition temperature, T MI and FM-PM transition temperature, T C increased with Sr content indicating the enhancement of double-exchange mechanism. Analysis of the resistivity change with respect to temperature, dlnρ/dT −1 versus T indicates onset of charge-ordering (CO) state where its CO transition temperature, T CO decreased with Sr content indicating weakening of the CO state. On the other hand, both absolute longitudinal and shear velocities as well as elastic moduli measured at 80 K increased significantly with Sr doping indicating improvement in elastic properties, which is suggested to be due to the increase in formation of ferromagnetic domains. A longitudinal velocity anomaly characterized by a slope change around the vicinity of T CO was observed for all samples. The longitudinal elastic anomaly is attributed to the Jahn–Teller (JT) effect of Mn3+ ions where analysis of the anomaly using the mean-field theory suggests involvement of the JT effect in the samples, which transforms from dynamic to static type with decreasing temperature. The elastic anomaly shifted down from 222 K (x=0) to 205 K (x=0.05) indicating that the static JT effect was weakened with Sr content. |
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