Phonon Transport Properties and Magnetic Transition in Perovskite Cobaltites

钙钛矿钴矿中的声子输运特性和磁转变

• 批准号: 14550661
• 负责人: FUJISHIRO Hiroyuki
• 金额: $ 1.79万
• 依托单位: IWATE UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550661/
• 关键词: Cobaltite Oxides; Spin Transition; Thermal Conductivity; Jahn-Teller Ions; Thermoelectric Materials; Phanon Scattering; Thermoelectric Power; Substitution Effect; 超巨大磁気抵抗; 熱拡散率; 強磁性転移

As recent revived studies on perovskite-based oxides have confirmed, RE_<1-X>A_XMO_3-type crystals (RE=rare earth ions, M=Mn, Co) 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 systems, however, the thermal (phonon) transport properties such as the thermal conductivity κ, thermal diffusivity α, and thermal dilatation dL/L have not been reported. In this study, we systematically measured these thermal transport properties of La_<1-X>AE_XCoO_3 (AE=Sr, Ca, Ba) crystals and investigated the phonon scattering mechanisms. The remarkable results are as follows ;(1)The thermal conductivity κ of the La_<1-X>Sr_XCoO_3 (X>0.2) system slightly enhances below the ferromagnetic transition temperature T_c, which is clearly understood on the basis of the increase in the electronic thermal conductivity κ_e. These results are contrast to those in La_<1-X>Sr_XMnO_3 (X>0.2), in which the relaxation of the Jahn-Teller (JT) distortion takes place below T_c.(2)The thermal conductivity κ of LaCoO_3 is markedly enhanced at 30K, however, the peak drastically decreases due to the substitution by the Sr^<2+> ions for the La^<3+> with 0.5% or by the Cu^<2+> and Ni^<2+> ions for the Co^<3+> with only 2%. It was found that the introduction of the Co^<4+> JT ions by the substitution seriously influences to the phonon transport.(3)The La_<1-X>Sr_XCoO_3 (0.1<X<0.15) system shows a promising candidate for the p-type thermoelecteric material around room temperatures, which is the phase boundary between the antiferromagnetic or spin-glass insulator and the ferromagnetic metal region.

近年来对钙钛矿型氧化物的研究证实，RE_<1-X>A_XMO_3型（RE=稀土离子，M=Mn，Co）晶体由于各种物理相互作用的相互作用和竞争，会发生多种相变。这些体系的电学、磁学和晶体学性质已经有了很多结果，但热导率κ、热扩散率α和热膨胀率dL/L等热（声子）输运性质还未见报道。在本研究中，我们系统地测量了La_<1-X>AE_XCoO_3（AE=Sr，Ca，Ba）晶体的这些热输运性质，并研究了声子散射机制。结果表明：（1）La_<1-X>Sr_xCoO_3（X&gt;0.2）体系的热导率κ在铁磁转变温度T_c以下略有增加，这是基于电子热导率κ_e的增加而得到的。这些结果与La_<1-X>Sr_xMnO_3（X&gt;0.2）中的结果相反，后者的Jahn-Teller（JT）畸变在低于T_c时发生弛豫。（2）LaCoO_3的热导率在30 K时有明显的提高，但由于Sr^&lt;2+&gt;离子取代了0.5%的La^&lt;3+&gt;或Cu^&lt;2+&gt;和Ni^&lt;2+&gt;离子取代了2%的Co^&lt;3+&gt;，热导率峰值急剧下降。结果表明，Co^&lt;4+&gt; JT离子的引入对声子输运产生了严重的影响。（3）La_<1-X>Sr_xCoO_3（0.1&lt;X&lt;0.15）体系是室温附近p型热电材料的理想候选者，它是反铁磁或自旋玻璃绝缘体与铁磁金属区之间的相界。

项目成果

Y.Fujine, H.Fujishiro, K.Suzuki, Y.Kashiwada, M.Ikebe: "Magnetism and thermoelectricity in La_<0.8>Sr_<0.2>Co_<1-Z>M_ZO_3(M : 3d transition metal)"J.Mag.Mag.Mat.. (to be published). (2004)

Y.Fujine、H.Fujishiro、K.Suzuki、Y.Kashiwada、M.Ikebe：“La_<0.8>Sr_<0.2>Co_<1-Z>M_ZO_3（M：3d 过渡金属）中的磁性和热电”J。

J.Hejtmanek, Z.Jirak, K.Knizek, M.Marysko, M.Veverka, H.Fujishiro: "Magnetism, structure and transport of Y_<1-X>Ca_XCoO_3"J.Mag.Mag.Mat.. (to be published). (2004)

J.Hejtmanek、Z.Jirak、K.Knizek、M.Marysko、M.Veverka、H.Fujishiro：“Y_<1-X>Ca_XCoO_3 的磁性、结构和传输”J.Mag.Mag.Mat..（至

J.Hejtmanek, Z.Jirak, K.Knizek, M.Marysko M.Veverka, H.Fujishiro: "Magnetism, structure and transport of Y_<1-X>Ca_XCoO_3 and La_<1-X>Ba_XCoO_3"J.Mag.Mag.Mat.. (to be published). (2004)

J.Hejtmanek、Z.Jirak、K.Knizek、M.Marysko M.Veverka、H.Fujishiro：“Y_<1-X>Ca_XCoO_3 和 La_<1-X>Ba_XCoO_3 的磁性、结构和传输”J.Mag。

J.Hejtmanek, Z.Jirak, K.Knizek, M.Marysko, M.Veverka, H.Fujishiro: "Magnetism, structure and transport in Y_<1-X>Ca_XCoO_3 and La_<1-X>Ba_XCoO_3."J.Mag.Mag.Mat.. (in press). (2004)

J.Hejtmanek、Z.Jirak、K.Knizek、M.Marysko、M.Veverka、H.Fujishiro：“Y_<1-X>Ca_XCoO_3 和 La_<1-X>Ba_XCoO_3 中的磁性、结构和传输。”J。

H.Fujishiro, Y.Fujine, J.Hejtmanek, D.Sedmidubsky, A.Maigan, C.Martin: "Search for p-type oxide thermoelectrics -- cobaltites"Proceedings of 21th International Conference on Thermoelectrics (ICT '03) IEEE. 192-195 (2004)

H.Fujishiro、Y.Fujine、J.Hejtmanek、D.Sedmidubsky、A.Maigan、C.Martin：“寻找 p 型氧化物热电材料——钴矿”第 21 届国际热电会议 (ICT 03) IEEE 论文集。