Development of room-temperature halfmetallic layered oxides

室温半金属层状氧化物的研制

• 批准号: 15206002
• 负责人: YAMAUCHI Hisao
• 金额: $ 26.37万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15206002/
• 关键词: Halfmetals; Spintronics; Transition-metal oxides; Double-perovskites; Mixed valence state; Mossbauer spectroscopy; FLAPW band calculations; スピンエレクトロニクス

Halfmetallic materials are anticipated to play a key role for emerging next-generational electronics called spintronics. Nonetheless only a handful number of such materials have been known to date. In the present research, development of new layered-oxide halfmetallic materials was conducted, consisting of the works on (1) search for new halfmetals, (2) development of high quality halfmetallic bulk materials and (3) quest for room-temperature halfmetals.(1)Novel halfmetals(1-1)BaRECo_2O_<5+δ>High-quality samples of oxygen-deficient layered double-perovskite oxides, BaRECo2O5+8 with RE=Nd, and Sin were synthesized by means of our original techniques which allow us to control the oxygen content with high accuracy, and studied in terms of magneto-transport and other related properties. In particular the sample, BaNdCo_20_<5.503> with δ = 0.503±0.003 exhibited large magneto-resistance of a tunneling-type for a temperature interval of 230 -260 K. Although the lower limit of this temperature … More interval shows due to the appearance of anti-ferromagnetism, the magnitude of MR at 230 K (a relatively high temperature) is as high as 12 % at 7 T. Thus this layered- oxide material was found to be halfmetallic at temperatures close to the ice point.(1-2)(LaMn)_<1-x>O_3Members of a new oxide family, (LaMn)_<1-x>O_3, were successfully synthesized employing a high-pressure technique. It was found that as had been predicted from a band calculation (by a (LSDA + U) method), (LaMn)_<0.901>O_3 was proven to show colossal magneto-resistance (CMR) below 250 K probably due to a double exchange mechanism. Our recent detailed study by neutron diffraction on the magnetic structure of this material supports the identification of this material as a halfmetal.(2)Homocomposites consisting of double-perovskite, Sr_2FeMoO_6A B-site ordered double-perovskite, Sr_2FeMoO_6 (SFMO), is known as a halfmetal (with T_C = 420 K). In order to improve the tunneling magneto-resistance characteristics of bulk halfmetals, an original concept of "homocomposite" was developed as a fashion of halfmetallic polycrystalline bulks. Two or more powders of different sizes of the same material are mixed before sintered into a homocomposite bulk. In such a bulk the grain contact is anticipated to be higher defined than in an ordinary ceramic bulk. The first halfmetallic homocomposite bulk was successfully fabricated for SFMO to yield excellent low-field tunneling magnetoresistance (LF-TMR) characteristics, e.g. ~5% at 0.5T at room temperature. It was found that the ratio of the smaller sized powder to the higher for the optimal LF-TMR is ~ 20%. It was considered that the nano-scale grain boundary is probably in a super-paramagnetic state yet while the grain inside is in a halfmetallic state.(3)Halfmetallic layered oxides at room temperatureIn previous sections (1) and (2) we reported discoveries of new halfmetals and development of halfmetallic bulks which show excellent LF-TMR at room temperature. None the less novel room-temperature halfmetallic layered oxides have not been obtained in this research. We believe that halfmetals of such nature are musts for spintronics and hope that further search for such halfmetals shall be continued, based on the results of the present project. Less

预计半金属材料将在新兴的下一代电子产品中发挥关键作用。尽管如此，迄今为止，只有少数几个此类材料。在本研究中，开发了新的分层半金属材料，包括（1）搜索新的半金属材料的作品，（2）开发高质量的半金属体积材料，（3）寻求室温的半度金属金属。氧化物，带有re = nd的bareco2O5+8，通过我们的原始技术合成了氧化物，使我们能够以高精度控制氧含量，并根据磁传输和其他相关特性进行了研究。特别是，样品the样品，δ= 0.503±0.003的样本表现出隧道类型的磁力较大的耐磁性，温度间隔为230 -260 k。尽管该温度的下限…更多的间隔显示，由于在230 k的高度上，该温度的高度显示出7个幅度为230 k的幅度，因此该温度高于230 k（均为230 k）（均为230 k的幅度）在靠近冰点的温度下，发现分层 - 氧化物的材料是半金属的。（1-2）（lamn）_ <1-x> o_3members的新氧化物家族（LAMN）_ <1-x> o_3，已成功地合成了使用高压力技术的合成。发现正如从频带计算（通过（LSDA + U）方法）所预测的那样，（LAMN）_ <0.901> O_3被证明显示出低于250 K以下的巨大磁耐药（CMR）可能是由于双重交换机制所致。我们最近通过中子衍射对该材料的磁性结构进行的详细研究支持将该材料鉴定为半金属。（2）由双植物，SR_2FEMOO_6A B位订购的双层植物套件组成的同质材料，SR_2FEMO_6A b sr_2femoo_6（sfmo），是一个半度性的（k），为了改善散装半金属的隧道磁力抗性特征，“同质复合材料”的原始概念是作为半金属多晶体散装的一种方式开发的。在将同一材料的两个或多个不同尺寸的粉末混合在一起，然后将其烧结成同质体积。在这样的大容量中，预计谷物接触的定义要高于普通陶瓷体积。成功制造了第一个半级同质复合材料，用于SFMO，以产生出色的低场隧穿磁磁力（LF-TMR）特性，例如在室温下0.5T时〜5％。发现最佳LF-TMR的较小粉末与较高的比率约为20％。据认为，纳米级晶界可能处于超副磁状态，而内部内部的谷物处于半金属状态。（3）在室温下（1）和（2），半金属分层的氧化物在室温下（1）和（2），我们报告了新的半金属和在室温下表现出极好的LF-TMR的半金属块的开发。在这项研究中，尚未获得新颖的室温半金属分层氧化物。我们认为，这种性质的半金属是Spintronics的必须的，并希望根据本项目的结果继续搜索此类半金属。较少的

项目成果

Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors : RuSr_2Gd_<1.5>Ce_<0.5>Cu_2O<10-δ> (Ru-1222) and RuSr_2GdCu_2O_8 (Ru-1212)

钌基磁超导体纳米域结构的电子显微镜研究：RuSr_2Gd_<1.5>Ce_<0.5>Cu_2O<10-δ> (Ru-1222) 和 RuSr_2GdCu_2O_8 (Ru-1212)

• 发表时间: 2004
• 期刊: Ultramicroscopy 98
• 作者: T.Yokosawa;V.P.S.Awana;K.Kimoto;E.Takayama-Muromachi;M.Karppinen;H.Yamauchi;Y.Matsui
• 通讯作者: Y.Matsui

V.P.S.Awana, M.Karppinen, H.Yamauchi: "Magneto-superconductivity in rutheno-cuprates RuSr_2GdCu_2O_<8-δ> (Ru-1212) and RuSr_2(Gd_<0.75>Ce_<0.25>)_2Cu_2O_<10-δ> (Ru-1222) : a critical review"In : International Book Series : Studies of High Temperature Supe

V.P.S.Awana、M.Karppinen、H.Yamauchi：“钌铜氧化物 RuSr_2GdCu_2O_<8-δ> (Ru-1212) 和 RuSr_2(Gd_<0.75>Ce_<0.25>)_2Cu_2O_<10-δ> (Ru -1222）：批判性评论“在：国际图书系列：高温超高温研究

M.Karppinen, K.Kotiranta, T.Nakane, S.C.Chang, J.M.Chen, R.S.Liu, H.Yamauchi: "Layer-specific hole concentrations in Bi_2Sr_2(Y_<1-x>Ca_x)Cu_2O_<8+δ> as probed by XANES spectroscopy and coulometric redox analysis"Physical Review B. 67. 134522-134527 (2003

M.Karppinen、K.Kotiranta、T.Nakane、S.C.Chang、J.M.Chen、R.S.Liu、H.Yamauchi：“Bi_2Sr_2(Y_<1-x>Ca_x)Cu_2O_<8+δ> 中层特定空穴浓度的探测通过 XANES 光谱和库仑氧化还原分析”Physical Review B. 67. 134522-134527 (2003

G.Peleckis, T.Motohashi, M.Karppinen, H.Yamauchi: "Enhanced thermoelectric properties of Na_xCoO_2 : whisker crystals"Applied Physics Letters. 83. 5416-5418 (2003)

G.Peleckis、T.Motohashi、M.Karppinen、H.Yamauchi：“Na_xCoO_2 的增强热电性能：晶须晶体”应用物理快报。

V.P.S.Awana, A.Gupta, H.Kishan, E.Takayama-Muromachi, T.Watanabe, M.Karppinen, H.Yamauchi, S.K.Malik, W.B.Yelon, V.Ganesan, A.V.Narlikar: "Superconductivity with transition temperature up to 80 K for TbSr_2Cu_<2.7>Mo_<0.3>O_<7+δ>"Solid State Communication

V.P.S.Awana、A.Gupta、H.Kishan、E.Takayama-Muromachi、T.Watanabe、M.Karppinen、H.Yamauchi、S.K.Malik、W.B.Yelon、V.Ganesan、A.V.Narlikar：“转变温度高达 80 的超导性K为TbSr_2Cu_<2.7>Mo_<0.3>O_<7+δ>》固态通讯