Phonon Scattering Mechanisms near Mott Transition in Highly Correlated Electron Systems

最近对钙钛矿基锰矿的研究已经证实，R_<1-X> a_xmnotau23epsilon2型晶体经历了各种各样的相变，这些相变源于各种物理相互作用的相互作用和竞争。这些锰矿石的电、磁和晶体学性质有许多结果，但热（声子）输运性质如导热系数kappa、热扩散系数alpha、声速upsilon_S和热膨胀dL/L尚未报道。在本研究中，我们测量了La Sr Mn 03 （LSMO）晶体（0.1 <X<0.9）的这些热输运性质，并研究了在铁磁转变温度T_C和变化有序温度T_<CO2>附近的声子散射机制。显著的结果如下：(1)声速upsilon_S异常与以X=1/8为中心的极化子有序温度T_P有关。upsilon_S是检测电荷排序的有力手段。(2) LSMO的导热系数kappa （X= 0）。在铁磁转变温度T0附近，在较宽的温度范围内显著降低。对1的分析揭示了异常强声子散射的存在。(3)我们证实了LSMO多晶在X=O附近发生了从铁磁绝缘体到反铁磁绝缘体的磁相变。第一次是50。(4) LSMO体系的声速upsilon_S和热膨胀dLIL的异常值（0.48<X<0.90）强烈提示了电荷有序的发生。(5)给出了La_<1-X>Sr_XMnO_3中电荷有序态随温度T和Sr浓度X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.