CAJ | 학술논문

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,出现了另一个超声衰减峰,它的出现归结为反铁磁相与顺磁相之间的相分离现象.随着Al在Mn位的掺入,超声声速的最低点和哀减峰向低温移动,表明体系中的电荷有序态和反铁磁相均被部分抑制.
계통연구료Nd0.5Ca0.5Mn1-xAlxO3(x=0,0.03)단상다정양품재저온하적전자성질화초성특성.전조화자화솔측량표명,Nd0.5Ca0.5O3체계재Tco～257 K처발생료전하유서상변.초성성속종실온개시수착온도적강저축점감소,병재Tco부근체도최소,지후,수착온도적진일보강저,성속급극증가,동시반수착일개첨예적초성쇠감봉출현.Tco부근적초성이상표명체계중존재착강렬적전-성자상호작용,해전-성자우합래원우Mn3+적Jahn-Teller 효응.재저온하,출현료령일개초성쇠감봉,타적출현귀결위반철자상여순자상지간적상분리현상.수착Al재Mn위적참입,초성성속적최저점화애감봉향저온이동,표명체계중적전하유서태화반철자상균피부분억제.
The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAixO3 (x=0,0.03) were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO～257 K. An obvious softening of the longitudinal sound velocity 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 separation 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 Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with Al.