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Ultrasonic Study on Charge Ordering in Nd0.5Ca0.5Mn1-xAlxO3 (x=0,0.03)
Yi Liu, Hui Kong, Jin-rui Su, Chang-fei Zhu*
Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China
Abstract:
The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 (x=0, 0.03) were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5Mn1-xAlxO3 undergoes a charge ordering transition at TCO?257 K. An obvious softening of the longitudinal sound ve- locity above TCO and a dramatic stiffening below TCO accompanied by an attenuation peak were observed. These features imply a strong electron-phonon interaction via the Jahn-Teller effect in the sample. Another broad attenuation peak was observed at around Tp?80 K. This anomaly is attributed to the phase separa- tion between the antiferromagnetic (AFM) and paramagnetic (PM) phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5Mn1-xAlxO3 are both partially suppressed by replacing Mn with Al.
Key words:  Manganite, Charge ordering, Phase separation, Ultrasonic velocity and attenuation
FundProject:supported by the National Natural Science Foundation of China (No.10274075) and the Specialized Research Fund for the Doctoral Program of Higher Education (No.20030358056)
附件
Nd0.5Ca0.5Mn1-xAlxO3 (x=0,0.03)体系中电荷有序态的超声研究
刘毅 , 孔辉 , 苏金瑞 , 朱长飞
中国科学技术大学材料科学与工程系,合肥230026
摘要:
系统研究了Nd0:5Ca0:5Mn1-xAlxO3 (x=0,0.03) 单相多晶 样品在低温下的电磁性质和超声特性. 电阻和磁化率测量表 明,Nd0:5Ca0:5O3体系在Tco?257 K处发生了电荷有序相变. 超声 声速从室温开始随着温度的降低逐渐减小,并在Tco附近达到最小, 之后,随着温度的进一步降低,声速急剧增加,同时伴随着一个尖锐 的超声衰减峰出现. Tco附近的超声异常表明体系中存在着强烈的电- 声子相互作用,该电-声子耦合来源于Mn3+的Jahn-Teller 效应. 在低 温下,出现了
关键词:  锰氧化物,电荷有序,相分离,超声声速与衰减
DOI:10.1360/cjcp2006.19(6).535.4
分类号: