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Journal Articles

Magnetic structure and local lattice distortion in giant negative thermal expansion material Mn $_{3}$ Cu $_{1-x}$ Ge $_{x}$ N

Iikubo, Satoshi*; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

Journal of Physics; Conference Series, 251, p.012014_1 - 012014_4, 2010/12

https://doi.org/10.1088/1742-6596/251/1/012014

Times Cited Count：4 Percentile：80.96(Biophysics)

Journal Articles

Gradual development of $Gamma^{5g}$ antiferromagnetic moment in the giant negative thermal expansion material MnCu $_{1-x}$ GeN ( 0.5)

Kodama, Katsuaki; Iikubo, Satoshi*; Takenaka, Koshi*; Takigawa, Masashi*; Takagi, Hidenori*; Shamoto, Shinichi

Physical Review B, 81(22), p.224419_1 - 224419_8, 2010/06

https://doi.org/10.1103/PhysRevB.81.224419

Times Cited Count：42 Percentile：81.37(Materials Science, Multidisciplinary)

Journal Articles

Lorentz transmission electron microscopy observation of magnetic domains in La $_{0.825}$ Sr $_{0.175}$ (Mn,Al)O $_{3}$

Mori, Shigeo*; Yoshidome, Kazuhiro*; Nagamine, Yuki*; Togawa, Yoshihiko*; Yoshii, Kenji; Takenaka, Koshi*

Journal of Applied Physics, 107(9), p.09D306_1 - 09D306_3, 2010/05

https://doi.org/10.1063/1.3358225

Times Cited Count：0 Percentile：0(Physics, Applied)

Nonmagnetic Al substitution effect on the stability of a ferromagnetic (FM) metallic state indouble-exchange manganite, La $_{0.825}$ Sr $_{0.175}$ MnO $_{3}$ , was investigated by Lorentz transmission electronmicroscopy (TEM), in combination with magnetic measurements. Both FM transition temperature(Tc) and the rhombohedral-to-orthorhombic (R-to-O) transition temperature (Ts) decreased by a few percent of Al substitution. An in situ Lorentz TEM observation revealed that drastic change of the FM domain structure took place through the R-to-O structural transition. The magnetization decreased slightly at Ts and characteristic spin-glass state is realized in the low-temperature region below Ts.

Journal Articles

Magnetic properties and ferromagnetic microstructures in Al-doped La $_{1-x}$ Sr $_{x}$ MnO $_{3}$

Mori, Shigeo*; Yoshidome, Kazuhiro*; Nagamine, Yuki*; Togawa, Yoshihiko*; Yoshii, Kenji; Takenaka, Koshi*

Journal of Physics; Conference Series, 200, p.012129_1 - 012129_4, 2010/02

https://doi.org/10.1088/1742-6596/200/1/012129

Times Cited Count：5 Percentile：84.49(Materials Science, Multidisciplinary)

Doping effect on ferromagnetic (FM) properties in perovskite manganites La $_{1-x}$ Sr $_{x}$ MnO $_{3}$ (x=0.175) were investigated by low-temperature Lorentz transmission electron microscopy (TEM), in combination with the conventional magnetic measurements. It is found that La $_{0.825}$ Sr $_{0.175}$ Mn $_{0.95}$ Al $_{0.05}$ O $_{3}$ exhibits a structural phase transition from the rhombohedral to orthorhombic structures at Ts116 K. During the rhombohedral-to-orthorhombic transition, the FM domain structures changed from the macroscopic FM domains to the FM ones with the wavy stripe pattern. The ac magnetic measurements also revealed that La $_{0.825}$ Sr $_{0.175}$ Mn $_{0.95}$ Al $_{0.05}$ O $_{3}$ shows unconventional magnetic behaviour at low temperature below 65 K. Partial substitution of non-magnetic Al $^{3+}$ for Mn $^{3+}$ has some influence on magnetic ordering and double-exchange interaction, which should induce insulator behaviour in the orthorhombic phase.

Journal Articles

Local structure anomaly around Ge dopants in Mn $_{3}$ Cu $_{0.7}$ Ge $_{0.3}$ N with negative thermal expansion

Matsuno, Jobu*; Takenaka, Koshi*; Takagi, Hidenori*; Matsumura, Daiju; Nishihata, Yasuo; Mizuki, Junichiro

Applied Physics Letters, 94(18), p.181904_1 - 181904_3, 2009/05

https://doi.org/10.1063/1.3129169

Times Cited Count：45 Percentile：82.5(Physics, Applied)

Local structure analysis of Cu and Ge atoms in the negative thermal expansion material Mn $_{3}$ Cu $_{0.7}$ Ge $_{0.3}$ N was conducted using X-ray absorption fine structure measurements. The temperature dependence of the interatomic distance was found to reflect the macroscopic negative thermal expansion both for Cu-Mn and Ge-Mn shells, although the magnitude of the relative change was much larger for Ge-Mn than Cu-Mn. An enhanced anomaly of the Debye-Waller factor was observed for the Ge-Mn shell in the temperature region of the negative expansion, indicating the presence of static local disorder around Ge impurities. These local structure anomalies strongly suggest that the local and inhomogeneous strain around Ge is essential in broadening the discontinuous volume contraction.

Journal Articles

Local lattice distortion in the giant negative thermal expansion material MnCu $_{1-x}$ GeN

Iikubo, Satoshi*; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Takigawa, Masashi*; Shamoto, Shinichi

Physical Review Letters, 101(20), p.205901_1 - 205901_4, 2008/11

https://doi.org/10.1103/PhysRevLett.101.205901

Times Cited Count：169 Percentile：96.65(Physics, Multidisciplinary)

Giant negative thermal expansion is achieved in antiperovskite manganese nitrides when the sharp volume change associated with magnetic ordering is broadened by substitution. In this Letter, we address the unique role of the "magic" element, Ge, for such broadening in MnCu $_{1-x}$ GeN. We present evidence for a local lattice distortion well described by the low-temperature tetragonal ( ${it T$_{4}$}$ ) structure of MnGeN for a range of , where the overall structure remains cubic. This structural instability shows a strong correlation with the broadness of the growth of the ordered magnetic moment and, hence, is considered to trigger the broadening of the volume change.

Journal Articles

Magnetovolume effect in MnCu $_{1-x}$ GeN related to the magnetic structure; Neutron powder diffraction measurements

Iikubo, Satoshi; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

Physical Review B, 77(2), p.020409_1 - 020409_4, 2008/01

https://doi.org/10.1103/PhysRevB.77.020409

Times Cited Count：109 Percentile：94.61(Materials Science, Multidisciplinary)

Magnetic structures in an antiperovskite system MnCu $_{1-x}$ GeN with a large magneto-volume effect above =0.15 have been studied by neutron powder diffraction measurement. The present neutron study revealed that not only a cubic crystal structure, but also a $Gamma^{5g}$ antiperovskite spin structure, is a key ingredient of the large magneto-volume effect in this itinerant electron system. The large magneto-volume effect is possibly ascribed to the geometrical frustration originating from the corner-shared octahedra of the antiperovskite sturucture.

Oral presentation

Magneto volume effect of Mn (Cu $_{1-x}$ Ge)N

Iikubo, Satoshi; Takenaka, Koshi*; Takagi, Hidenori*; Kodama, Katsuaki; Shamoto, Shinichi

no journal, ,

In the Mn nitride MnAN system, there are several compound that the lattice constant increase as a first-order transition at low temperature below magnetic ordering temperature. Among this system, It was found that this transition becomes broad and occurs around room temperature in MnCu $_{1-x}$ GeN for x 0.5. This property is focused in view of application use as the negative thermal expansion material. We have studied the magnetism and local crystal structure by neutron scattering technique. We would like to discuss the mechanism of occurrence of negative thermal expansion.

Oral presentation

Magneto volume effect of MnCu $_{1-x}$ GeN

Iikubo, Satoshi; Takenaka, Koshi*; Kodama, Katsuaki; Takagi, Hidenori*; Shamoto, Shinichi

no journal, ,

Crystal and magnetic structures of the anti-perovskite system MnCu $_{1-x}$ GeN, which show large negative thermal expansion coefficients around the room temperature have been investigated by the neutron diffraction study. Obtained results indicate that the cubic crystal structure and $Gamma^{5g}$ anti-ferromagnetic structure are essential for large magneto-volume effect in this system. In the MnCu $_{0.5}$ Ge $_{0.5}$ N, experimental evidences of coexistence of two magnetic structure, $Gamma^{5g}$ and $Gamma^{4g}$ anti-ferromagnetic structures are revealed around room temperature where the colossal negative thermal expansion coefficient appears.

Oral presentation

Magnetic structure of Mn(Cu $_{1-x}$ Ge)N

Iikubo, Satoshi; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

no journal, ,

no abstracts in English

Oral presentation

Neutron scattering study of giant negative thermal expansion material MnCu $_{1-x}$ GeN

Iikubo, Satoshi; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

no journal, ,

no abstracts in English

Oral presentation

NMR study on MnCu $_{1-x}$ GeN with large negative thermal expansion

Kodama, Katsuaki; Takigawa, Masashi*; Iikubo, Satoshi; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

no journal, ,

Anti-peroveskite system MnCu $_{1-x}$ GeN exhibits a sharp volume expansion due to the magneto-volume effect at . With increasing , the magneto-volume effect is broadened against temperature , and as a result, the volume expansion becomes almost linear to and the system has a giant negative thermal expansion coefficient arround room temperature, at . Such broadening of the magneto-volume effect may be due to the competitation between $Gamma^{5g}$ - and $Gamma^{4g}$ -type antiferromagnetic structures. Then we have performed $^{14}$ N-NMR on MnCu $_{0.6}$ Ge $_{0.4}$ N in order to investigate the origin of the broadening of the magneto-volume effect. The experimental results show that $Gamma^{4g}$ -type antiferromagnetic structre does not exist and $Gamma^{5g}$ -type antiferromagnetic ordered moment continuously increases with decreasing .

Oral presentation

Neutron scattering study of giant negative thermal expansion material MnCu $_{1-x}$ GeN

Iikubo, Satoshi; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

no journal, ,

no abstracts in English

Oral presentation

Magnetic structures and magneto-volume effects in MnCu $_{1-x}$ GeN

Iikubo, Satoshi; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

no journal, ,

no abstracts in English

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Magnetic structure and local lattice distortion in giant negative thermal expansion material Mn $_{3}$ Cu $_{1-x}$ Ge $_{x}$ N

Gradual development of $Gamma^{5g}$ antiferromagnetic moment in the giant negative thermal expansion material MnCu $_{1-x}$ GeN ( 0.5)

Lorentz transmission electron microscopy observation of magnetic domains in La $_{0.825}$ Sr $_{0.175}$ (Mn,Al)O $_{3}$

Magnetic properties and ferromagnetic microstructures in Al-doped La $_{1-x}$ Sr $_{x}$ MnO $_{3}$

Local structure anomaly around Ge dopants in Mn $_{3}$ Cu $_{0.7}$ Ge $_{0.3}$ N with negative thermal expansion

Local lattice distortion in the giant negative thermal expansion material MnCu $_{1-x}$ GeN

Magnetovolume effect in MnCu $_{1-x}$ GeN related to the magnetic structure; Neutron powder diffraction measurements

Magneto volume effect of Mn (Cu $_{1-x}$ Ge)N

Magneto volume effect of MnCu $_{1-x}$ GeN

Magnetic structure of Mn(Cu $_{1-x}$ Ge)N

Neutron scattering study of giant negative thermal expansion material MnCu $_{1-x}$ GeN

NMR study on MnCu $_{1-x}$ GeN with large negative thermal expansion

Neutron scattering study of giant negative thermal expansion material MnCu $_{1-x}$ GeN

Magnetic structures and magneto-volume effects in MnCu $_{1-x}$ GeN