Development of room-temperature halfmetallic layered oxides

室温半金属层状氧化物的研制

基本信息

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

项目摘要

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

半金属材料预计将在称为自旋电子学的新兴下一代电子学中发挥关键作用，但迄今为止，在目前的研究中，开发了新型层状氧化物半金属材料。致力于 (1) 寻找新的半金属，(2) 开发高质量半金属块状材料，以及 (3) 寻找室温半金属。(1)新颖halfmetals(1-1)BaRECo_2O_<5+δ>通过我们独创的技术合成了高质量的缺氧层状双钙钛矿氧化物样品，BaRECo2O5+8（RE=Nd）和Sin，这使我们能够控制氧含量高精度，并研究了磁输运和其他相关特性，特别是样品 BaNdCo_20_<5.503>，δ = 0.503±0.003 在 230 -260 K 的温度区间表现出隧道型的大磁阻。尽管该温度区间的下限显示出由于反铁磁性的出现，但 230 K 时的 MR 大小（相对较高的温度）在 7 T 时高达 12%。因此，发现这种层状氧化物材料在接近冰点。(1-2)(LaMn)_<1-x>O_3 采用高压技术成功合成了新氧化物家族的成员(LaMn)_<1-x>O_3。通过能带计算（通过（LSDA + U）方法）预测，（LaMn）_<0.901>O_3被证明表现出巨大的磁阻（CMR）低于 250 K 可能是由于双交换机制所致。我们最近通过中子衍射对该材料的磁结构进行了详细研究，支持将该材料鉴定为半金属。(2)由双钙钛矿、Sr_2FeMoO_6A B 位有序组成的均质复合材料。双钙钛矿，Sr_2FeMoO_6 (SFMO)，被称为半金属（T_C = 420 K）。为了改善块体半金属的隧道磁阻特性，“均质复合材料”的原始概念被开发为半金属多晶块体的一种形式，将两种或多种不同尺寸的相同材料的粉末混合，然后烧结成均质复合材料块体。这种块体的晶粒接触预计比普通陶瓷块体的定义更高第一个半金属均质复合块体已成功为 SFMO 制造，以产生优异的性能。低场隧道磁阻 (LF-TMR) 特性，例如在室温下 0.5T 时，较小尺寸粉末与较大尺寸粉末的比例约为 20%。认为纳米级晶界可能处于超顺磁性状态，而内部晶粒处于半金属状态。 (3)室温下的半金属层状氧化物在第（1）和（2）节中，我们报告了新半金属的发现以及在室温下表现出优异的 LF-TMR 的半金属块体的开发，但我们认为，本研究尚未获得新颖的室温半金属层状氧化物。这种性质的半金属是自旋电子学的必需品，希望根据当前项目的结果继续进一步寻找这种半金属。

项目成果

期刊论文数量（361）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Magneto-superconductivity of 100-atm O_2-annealed RuSr_2Gd_<1.5>Ce_<0.5>Cu_2O_<10-δ>

100-atm O_2退火RuSr_2Gd_<1.5>Ce_<0.5>Cu_2O_<10-δ>的磁超导性

DOI：
发表时间：
2003
期刊：
Physica C 390
影响因子：
0
作者：
V.P.S.Awana;E.Takayama-Muromachi;M.Karppinen;H.Yamauchi
通讯作者：
H.Yamauchi

Systematic induction of superconductivity in the Cu(Y_<1-x>Ca_x)Ba_2Cu_2O_<6+δ> (δ【apploximately equal】0.3) system by Ca substitution

Cu(Y_<1-x>Ca_x)Ba_2Cu_2O_<6+δ>(δ【约等于】0.3)体系中Ca取代系统诱导超导

DOI：
发表时间：
2005
期刊：
な 18
影响因子：
0
作者：
V.P.S.Awana;M.A.Ansari;R.Nigam;A.Gupta;S.B.Samanta;R.B.Saxena;H.Kishan;V.Ganesan;A.V.Narlikar;M.Arai;M.Karppinen;H.Yamauchi;D.Buddhikot;S.K.Malik
通讯作者：
S.K.Malik

Exploring the Verwey-type transition in GdBaFe_2O_<5+w> using ^<57>Fe Mossbauer spectroscopy

使用 ^<57>Fe 穆斯堡尔谱探索 GdBaFe_2O_<5 w> 中的 Verwey 型转变

DOI：
发表时间：
2004
期刊：
Hyperfine Interactions 156
影响因子：
0
作者：
J.Linden;P.Karen;H.Yamauchi;M.Karppinen
通讯作者：
M.Karppinen

Transport and magnetotransport properties across the two-step Verwey transition in BaGdFe_2O_<5+w>

BaGdFe_2O_<5 w> 中两步 Verwey 转变的输运和磁输运特性

DOI：
发表时间：
2006
期刊：
Physical Review B 73
影响因子：
0
作者：
J.Linden;P.Karen;J.Nakamura;M.Karppinen;H.Yamauchi
通讯作者：
H.Yamauchi

Magnetism in Na_<0.75>CoO_2 investigated by μSR

μSR研究Na_<0.75>CoO_2中的磁性

DOI：
发表时间：
2004
期刊：
Transact. Mater. Res. Soc. Jpn. 29
影响因子：
0
作者：
J.Sugiyama;H.Itahara;J.H.Brewer;E.J.Ansaldo;T.Motohashi;M.Karppinen;H.Yamauchi
通讯作者：
H.Yamauchi