Effect of Er substitution on ultrasonic anomaly in Dy0.5-xErxBa0.5CoO3 cobaltates
Rare-earth cobaltates Dy0.5-xErxBa0.5CoO3 (x = 0, 0.03 and 0.05) have been systematically investigated to elucidate the effect of Er substitution on elastic as well as magnetic and transport properties. DC electrical resistance and AC susceptibility measurements showed that the x = 0 sample exhibite...
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| Format: | Article |
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Elsevier
2013
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| Online Access: | http://www.elsevier.com/ locate/ultras http://www.elsevier.com/ locate/ultras http://eprints.uthm.edu.my/8160/1/dr_suhadir.pdf |
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| Summary: | Rare-earth cobaltates Dy0.5-xErxBa0.5CoO3 (x = 0, 0.03 and 0.05) have been systematically investigated to
elucidate the effect of Er substitution on elastic as well as magnetic and transport properties. DC electrical
resistance and AC susceptibility measurements showed that the x = 0 sample exhibited an insulating
behavior and an anti-ferromagnetic (AFM) transition, TN at 198 K as well as ferromagnetic (FM) transition,
TC at 260 K. Increasing of Er content suppressed the FM and AFM state suggestively due to the
increase in size disorder arising from the size mismatch between A-site cations as shown from our calculation
of variance r2. On the other hand, both absolute longitudinal and shear velocities and related
elastic moduli measured at 210 K decreased with Er content in conjunction with the declining in the
FM domain indicating a weakening in elastic properties. A longitudinal velocity anomaly characterized
by a drop in velocity upon cooling before hardening with further cooling was observed for all samples.
This abnormal elastic anomaly can be attributed due to the Jahn–Teller (JT) distortion of intermediatespin
Co3+ ions. Analysis of the elastic anomaly using the mean-field theory suggested that it is related
to the JT effect which transformed from dynamic to static type with decreasing temperature. The elastic
anomaly shifted to lower temperature from 129 K (x = 0) to 124 K (x = 0.05) with Er substitution indicating
a weakening of the static JT effect. |
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