Phonon Scattering Mechanisms near Mott Transition in Highly Correlated Electron Systems

最近对钙钛矿基锰氧化物的研究证实，R_<1-X>A_XMnOTAU23EPSILON2型晶体经历了各种相变，这些相变源于各种物理相互作用的相互作用和竞争。这些锰氧化物的电学、磁学和晶体学性质已有很多研究结果，但其热（声子）输运性质如热导率kappa、热扩散率α、声速uppermost_S和热膨胀率dL/L等尚未见报道。本文测量了LaSrMn 03（LSMO）晶体（0.1 &lt;X&lt;0.9）的热输运性质，并研究了在铁磁转变温度T_C和有序转变温度T_C附近的声子散射机制<CO2>。（1）观察到声速uppermost_S异常，它与中心在X=1/8处的极化子有序温度T_P有关。uppermost_S是检测电荷有序性的有力手段。（2）LSMO（X= 0.17和0.155）的热导率kappa在铁磁转变温度T0附近的较宽温度范围内显著降低。对1的分析揭示了强声子散射的存在。(3)We首次证实了LSMO多晶在X= 0.50附近从铁磁绝缘体到反铁磁绝缘体的磁相变。（4）LSMO系统的声速uppermost_S和热膨胀dLIL（0.48&lt;X&lt;0.90）的异常强烈地暗示了电荷有序的存在。(5)A提出了La_ Sr_xMnO_3中电荷有序态<1-X>随温度T和Sr浓度X变化的相图。

As recent revived studies on perovskite-based manganites have confirmed, R_<1-X>A_XMnOTAU23EPSILON2-type crystals undergo a variety of phase transitions which originate from the interplay and competition of various physical interactions. There are many results of electric, magnetic and crystallographic properties in these manganites, however, the thermal (phonon) transport properties such as the thermal conductivity kappa, thermal diffusivity alpha, sound velocity upsilon_S and thermal dilatation dL/L have not been reported. In this study, we measured these thermal transport properties of La Sr Mn 03 (LSMO) crystals (0.1 <X<0.9) and investigated the phonon scattering mechanisms near the ferromagnetic transition temperature T_C and the change ordering temperature T_<CO2>.The remarkable results are as follows ;(1)The sound velocity upsilon_S anomaly has been observed which is related to the polaron-ordering temperature T_P centered at X=1/8. The upsilon_S is the powerful measure to detect the charge ordering.(2)The thermal conductivity kappa of LSMO (X=O.1 7 and 0.155) is markedly reduced over a wide temperature range near the ferromagnetic transition temperature T0. The analyses of 1 have revealed the existence anomalously strong phonon scattering.(3)We confirmed the magnetic phase transition from a ferromagnetic insulator to an antiferromagnetic insulator in LSMO polycrystals at around X=O.50 for the first time.(4)The anomalies of the sound velocity upsilon_S and thermal dilatation dLIL of LSMO system (0.48<X<0.90) strongly suggest the occurrence of the charge ordering.(5)A phase diagram of the charge-ordered state in La_<1-X>Sr_XMnO_3 as a function of temperature T and the Sr concentration X is proposed.