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Ultrasonic Study on Jahn-Teller Distortions in La1=3Sr2=3CoO3
Jian-xing Yi,Hui Kong,Chang-fei Zhu*
Author NameAffiliationE-mail
Jian-xing Yi Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engi- neering, University of Science and Technology of China, Hefei 230026, China  
Hui Kong Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engi- neering, University of Science and Technology of China, Hefei 230026, China  
Chang-fei Zhu* Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engi- neering, University of Science and Technology of China, Hefei 230026, China cfzhu@ustc.edu.cn 
Abstract:
The longitudinal ultrasonic velocity (Vl), attenuation (ffl), magnetization and resistivity of single phase polycrystalline La1=3Sr2=3CoO3 were measured as a function of temperature from 20 K to 300 K. The resistivity shows metallic behavior in the whole temperature range and a kink at 235 K was observed, which coincides with the ferromagnetic transition temperature (Tc). As the temperature cools down from Tc, the Vl softens conspicuously at beginning and reaches a minimum at 120 K. After that the Vl dramatically stiffens below 120 K accompanied by a wide attenuation peak. The analysis of the results suggests that these ultrasonic anomalies may correspond to local lattice distortions via the Jahn-Teller effect of intermediate spin Co3+.
Key words:  La1=3Sr2=3CoO3, Ultrasonic velocity and attenuation, Jahn-Teller e?ect
FundProject:国家自然科学基金(No.10274075) 高等学校博士点专项科研基金(No. 20030358056)
Ultrasonic Study on Jahn-Teller Distortions in La1=3Sr2=3CoO3
蚁建兴,孔辉,朱长飞*
摘要:
系统研究了La1=3Sr2=3CoO3单相多晶样品在低温下的电磁输运性质和超声特性.电阻率测量表明,La1=3Sr2=3CoO3在整个温区内都表现出金属特性,并且在235 K处电阻率-温度曲线的斜率发生了变化,同时伴随着铁磁相变.超声声速在铁磁相变温度以下出现软化,并在120 K附近达到最小,之后,随着温度的进一步降低,声速开始硬化,同时出现了一个宽大的超声衰减峰.分析认为,该超声异常可能起源于中等自旋态Co3+的Jahn-Teller效应.
关键词:  钴氧化物,超声声速和衰减,Jahn-Teller效应
DOI:10.1088/1674-0068/21/02/136-140
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