構成

助教授

的場正憲

博士課程

岡田悟志，岡部博孝，神原陽一，竹内弾正

修士課程

伊藤秀樹，加納忠彦，村上嘉弘，榎本康太郎，中野克哉，畠澤崇，松井雅博

学部

竹下之典，猪植康弘，伊藤理敬，大山博正，茂木祐介，竹下之典，野原裕紀

研究成果

1. Magnetic Nature in NaxCoO2

Magnetic properties in Na0.75CoO2 (space group P63/mmc) are investigated by DC magnetic measurements from 2 to 300 K. The temperature-dependent magnetic susceptibility data show Curie-Weiss behaviour down to 15 K. Spin glass like characteristics are also found; the cusp anomaly seen at 3 K, irreverisbility between zero-field and field cooled magnetic susceptibility below 13 K.

2. Magnetism of Layered Cobalt Oxysulfide Sr2Cu2CoO2S2

Magnetic and electronic nature have been investigated for the novel layered oxysulfide Sr2Cu2CoO2S2 (space group I/4mmm). Sr2Cu2CoO2S2 is the antiferromagnet with TN (=200 K) determined by the measurements of neutron powder diffraction and magnetic susceptibility (χ). The dχ/dT shows a broad maximum indicative of two-dimensional antiferromagnetic nature, which is not originated from the (Cu+S)2 layers but the strongly correlated Co2+O2 square-planes revealed by the X-ray photoemission spectroscopy.

3. Magnetic Dilution and Electronic Nature in La0.7Pb0.3Mn1-yZnyO3

We have studied the magnetic dilution and electronic nature of Zn doping on the Mn site in the colossal magnetoresistant material La0.7Pb0.3MnO33 (x<0.3). Small non-magnetic Zn2+ doping tends to separate the system into ferromagnetic clusters to weaken the long-range ferromagnetic order and to reduce the Curie temperature. The spin polarizability of the x=0～0.3 samples is estimated to be 0.97～1.00, indicating that the x=0～0.3 samples are the spin polarized materials in which the conductivity is dominated by single-spin charge carriers. Small doping (x<0.1) induces the metal-insulator transition and destroys the metallic state with long-range ferromagnetic order.

4. Pressure effect on magnetic nature of Sr2Cu2CoO2S2

We have studied pressure effects on the magnetic and electronic nature of layered oxysulfide Sr2Cu2CoO2S2 which crystallizes in an unusual intergrowth structure. The derivative permeability dμ/dT curves have a kink near Tt at which the antiferromagnetic nature is changed from 2D to 3D; Tt extremely rises with increasing pressure (dTt/dP=13.5 K/kbar), indicating that 3D antiferromagnetic state is more stable under pressure. The Tt in the dμ/dT curves correspond to the bending point of the resistivity, and above Tt the nearest-neighbor hopping conduction occurs. These features would be discussed from the viewpoint of the coupled nature of charge carriers and 2D antiferromagnetic spin ordering.

5. Magnetic properties of novel layered oxysulfide Sr2Cu2(Co,Cu)O2S2

We have studied the magnetic properties of layered oxysulfide Sr2Cu2(Co,Cu)O2S2 with the (Co,Cu)O2 planes. Magnetic susceptibility shows a broad maximum indicative of two-dimensional antiferromagnetic nature above 140K. Below 80K, the divergence between zero-field cooled and field cooled magnetizations is seen; long time decay is observed at 10 and 75K, while it is not observed at 45K. These feature is discussed from the viewpoint of the strongly and frustrated spin system which is different from the traditional spin glass.

6. Magnetic and electronic nature of layered manganese oxysulfide Sr2CuMnO3S

We have synthesized and investigated the magnetic and electronic nature of layered manganese oxysulfide Sr2CuMnO3S which crystallizes in an unusual intergrowth structure with Cu2S2 and pyramidal MnO5 layers separated by Sr ions. A Cu 2p x-ray photoemission spectroscopy (XPS) spectrum of Sr2CuMnO3S indicates that the Cu ion is in the monovalent state, or Cu+. This feature of the Mn 2p XPS spectrum of Sr2CuMnO3S is similar to that of the parent compound La3+Mn3+O3 of colossal magnetoresistance materials. The MnO5 cluster model analysis suggests that the electronic nature of the pyramidal MnO5 layers belongs to a strongly correlated electron system, and the system is the so-called Mott insulator resulting from the strongly correlated electron nature. Magnetic susceptibility exhibits low-dimensional antiferromagnetic ordering of Mn3+ in pyramidal MnO5 layers. Fitting the data to Curie-Weiss law provides the evidence of strong second neighbor Mn-Mn interaction.

発表論文・学会発表・特許申請など

発表論文

  1. Tadamasa Takeuchi, Masanori Matoba, Tomoko Aharen, and Mitsuru Itoh: “Magnetic Anomalies in NaxCoO2 (x=0.75)”, Physica B312-313 (2002) 719-720.
  2. Masanori Matoba, Tadamasa Takeuchi, Satoshi Okada, Youichi Kamihara, Mitsuru Itoh, Kenji Ohoyama, and Yasuo Yamaguchi: “Magnetism of Novel Layered Cobalt Oxysulfide Sr2Cu2CoO2S2 with Strongly Correlated CoO2 Square-Planes”, Physica B312-313 (2002) 630-631.
  3. Tadahiko Kanoh and Masanori Matoba: “Magnetic Dilution and Electronic Nature in La0.7Pb0.3Mn1-yZnyO3”, Journal of Physics and Chemistry of Solids 63 (2002) 935-937.
  4. Satoshi Okada, Masanori Matoba, Hajime Yoshida, Kenji Ohoyama, and Yasuo Yamaguchi: “Pressure effect on magnetic nature of Sr2Cu2CoO2S2 with strongly correlated CoO2 square-planes”, Journal of Physics and Chemistry of Solids 63 (2002) 983-985.
  5. Satoshi Okada, Masanori Matoba, Youich Kamihara, Tadamasa Takeuchi, Satoshi Fukumoto, Shunji Soyano, Hajime Yoshida, Kenji Ohoyama, and Yasuo Yamaguchi: “Magnetic properties of novel layered oxysulfide Sr2Cu2(Co,Cu)O2S2 with Cu-doped CoO2 square-planes”, Journal of Applied Physics 91 (2002) 8861-8863.
  6. Youich Kamihara, Masanori Matoba, Toru Kyomen, and Mitsuru Itoh: “Magnetic and electronic nature of novel layered manganese oxysulfide Sr2CuMnO3S”, Journal of Applied Physics 91 (2002) 8864-8866.
  7. 加納忠彦, 神原陽一，的場正憲: “La0.7Pb0.3Mn1-yZnyO3における金属－非金属転移とZnによる磁気希釈”, 日本応用磁気学会誌 26 (2002) 368-371.
  8. 神原陽一, 岡田悟志, 的場正憲: “層状Mn酸化硫化物Sr2CuMnO3Sの物性”, 日本応用磁気学会誌 26 (2002) 372-375.
  9. 長沼順子, 神原陽一，的場正憲: “新規な無機ハイブリッド型層状遷移金属硫化酸化物ペロブスカイト関連酸化物Sr2Cu(Fe,Ga)O3S および(Sr,La)4Cu2Mn3O7.5S2の合成と評価”, 日本応用磁気学会誌 26 (2002) 376-379.

学位論文

博士論文

岡田悟志：強相関電子系CoO2平面を有する層状オキシ硫化物半導体の合成と物性 [主査：的場正憲，副査：安西修一郎，太田英二，椎木一夫]

修士論文

伊藤秀樹：AB2O6(A=Cu,Co,Mn,Mg,Sr;B=Nb,Sb,Ta)の開発と物性評価
加納忠彦：La0.7R0.3MnO3(R=Pb,Sr,Ca)のスピン電荷複合物性に対するZnドーピング効果
村上嘉弘：n型希薄磁性熱電半導体(Zn1-xMx)Sb2O6(M=Mn,Fe,Co)の開発と評価

卒業論文

竹下之典：スピネル型遷移金属硫化物の合成と評価
猪植康弘：層状硫化物NbS2におけるインターカーレーションとその効果
伊藤理敬：(Cu,Ga)Sb2O6の結晶構造と強相関電子物性
大山博正：層状コバルト酸化硫化物の高圧物性
野原裕紀：高効率n型熱電変換酸化物Cd3TeO6の開発と評価
茂木祐介：ペロブスカイト型ルテニウム酸化物Na0.5La0.5RuO3の合成と評価

進路

早稲田大学理工学部応用物理学科博士研究員
慶應義塾大学大学院理工学研究科
日本電気
シャープ
石川島播磨重工業

研究助成

旭硝子財団，「人と環境に調和した熱電エネルギー変換素子の創製」

慶應義塾大学学事振興資金(共同研究)，「ナノ空間デザインによる量子機能の開拓と高度機能材料設計」