Ultrasonic anomaly near the charge ordering transition in Sr-doped Nd0.3La0.2Ca0.5−xSrxMnO3 manganites
Sr doping in the charge-ordered compound Nd0.3La0.2Ca0.5−xSrxMnO3 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, χ1 measurements showed all sa...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Published: |
Springer US
2013
|
| Subjects: | |
| Online Access: | DOI:10.1007/s10948-013-2389-8 DOI:10.1007/s10948-013-2389-8 |
| Summary: | Sr doping in the charge-ordered compound
Nd0.3La0.2Ca0.5−xSrxMnO3 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, χ1
measurements showed all samples exhibit metal-insulator
(MI) behavior accompanied by ferromagnetic-paramagnetic
(FM-PM) transition where the MI transition temperature,
TMI and FM-PM transition temperature, TC increased with
Sr content indicating the enhancement of double-exchange
mechanism. Analysis of the resistivity change with respect
to temperature, d lnρ/dT
−1 versus T indicates onset of
charge-ordering (CO) state where its CO transition temperature,
TCO 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 TCO 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. |
|---|