H. Onodera
Tohoku University
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Featured researches published by H. Onodera.
Journal of Magnetism and Magnetic Materials | 1983
H. Yamamoto; H. Onodera; K. Hosoyama; Tsuyoshi Masumoto; H. Yamauchi
Abstract Magnetic properties of amorphous Fe92Zr8 and Fe90Zr10 alloys have been studied by 57Fe Mossbauer and magnetization measurements. The magnetic hyperfine field distribution spreads over a wide range and the temperature dependence of the hyperfine fields shows magnetically heterogeneous behavior. Superparamagnetic behavior was observed on the magnetization curves above Tc.
Journal of Magnetism and Magnetic Materials | 1999
H. Shiraishi; Hiroshi Niida; Y. Iguchi; S. Mitsudo; M. Motokawa; K. Ohayama; Hiroshi Miki; H. Onodera; T. Hori; Kazuo Kanematsu
Abstract New intermetallic compounds (Mn 1 − x Ni x ) 65 Ga 35 of Ni 2 In type structure are found in the range of 0.15 ⩽ x ⩽ 0.45. In the higher x range, the magnetization—temperature curves show Curie—Weiss type behaviors, but those with x ⩽ 0.35 suggest another type ferromagnet. The magnetic ordering temperature T c decreases for x ⩽ 0.2 and then increases with increasing x . The curves of 0.25 ⩽ x ⩽ 0.3 show a hump and then slightly decrease with decreasing temperature. In the neutron diffraction experiment for x = 0.275, the (0 0 1) reflection appears for 165 K ⩽ T T C to 8.47 C with temperature.
Journal of Magnetism and Magnetic Materials | 1997
Dong-Liang Peng; Toyohiko J. Konno; Kenji Sumiyama; H. Onodera; K. Suzuki
Structure and magnetic properties of FenCrnN ternary films prepared by DC magnetron facing-target sputtering have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mossbauer effect. These films exhibit perpendicular magnetic anisotropy. We found that N2-to-Ar flow ratio, Fe-Cr target area ratio and substrate temperature during film preparation are the factors influencing the anisotropy. Adjusting the chemical composition and deposition parameters, we obtained saturation magnetization of 300–400 emu/cm3 and perpendicular coercivity of 800–1100 Oe. XRD measurements show that the films generally consist of the α-Fe(Cr) and γ′-(Fe,Cr)4Nx (x < 1) phases, and that the enhancement of perpendicular anisotropy is always accompanied by a decrease in the grain size of α-Fe(Cr) phase and growth of the γ′-(Fe,Cr)4Nx phase with a pronounced (2 0 0) texture. The Mossbauer spectra show that the γ′-(Fe,Cr)4Nx phase is nonmagnetic at room temperature. Using the SEM and TEM, we found that the nonmagnetic γ′-(Fe,Cr)4Nx phase displays columnar growth and that the small ferromagnetic α-Fe(Cr) grains of about 2–20 nm in diameter are located at grain boundaries of γ′-(Fe,Cr)4Nx grains. Shape anisotropy seems to play an important part in the perpendicular magnetic anisotropy in these FenCrnN films.
Journal of Magnetism and Magnetic Materials | 1998
H. Shiraishi; T. Hori; Hidemi Kato; H. Onodera; Y. Yamaguchi; Kazuo Kanematsu
Abstract The high-temperature phase of (Ni 1 - x Mn) 1.9 Ge is found to be a hexagonal Ni 2 In type structure in the range 0 ⩽ x ⩽ 0.7. In the lower values of x , spin glass and re-entrant spin-glass phase was found. In the range 0.55 ⩽ x ⩽ 0.7, the alloys are ferromagnetic and the Curie temperature decreases with increasing x . A phase transition of Ni 2 In type ⇔TiNiSi type occurs at 0.45 ⩽ x ⩽ 0.55, below 270K. Magnetic and crystallographic phase diagram is proposed.
Journal of Magnetism and Magnetic Materials | 1995
Hisao Kobayashi; Masayoshi Ohashi; H. Onodera; Takahito Ono; Y. Yamaguchi
Abstract The magnetic phase transitions in DyMn 2 Ge 2 were studied by neutron diffraction. The (111) antiferromagnetic order reflection due to Mn atoms is observed only above 40 K, and the intermediate superlattice (110) ± line is observed in the temperature range between 35 and 40 K. It is concluded that the intermediate temperature phase is a magnetically single phase in which the magnetic stracture is described with a propagation vector k ≈ (0, 0, 0.65).
Journal of Magnetism and Magnetic Materials | 1998
T. Hori; Hiroshi Niida; Kouji Ohyama; Masayoshi Ohashi; H. Onodera; Y. Yamaguchi; Hiroaki Kato; Y. Nakagawa
Abstract We have found that the ferromagnetic alloys (Fe 1- x ,Mn x ) 3 Ga of a D0 3 -type structure are stable up to x = 0.5. A partially ordered L2 1 -type structure is confirmed by neutron diffraction experiments. The magnetization decreases monotonically with increasing x . The Curie temperature has a minimum value of 200 K at x = 0.35. The average magnetic moment per (Fe or Mn) atom in the 4b site keeps nearly a constant value of 1.7 μ B , and that in the 8c site decreases rapidly with increasing x , showing negative valules for x ⩾ 0.4. In addition to the saturation magnetization, large paramagnetic components are observed in high magnetic fields.
Journal of Physics and Chemistry of Solids | 1999
Takahiro Onimaru; H. Onodera; Kenji Ohoyama; H. Yamauchi; Masayoshi Ohashi; Y. Yamaguchi
Journal of Magnetism and Magnetic Materials | 2007
Toshiya Inami; T. Honma; Satoshi Tsutsui; Kentaro Indoh; H. Onodera; Kenji Ishii; Kenji Ohwada; K. Kuzushita; H. Nakao; Youichi Murakami
Journal of Magnetism and Magnetic Materials | 2007
Satoshi Tsutsui; Hisao Kobayashi; A.Q.R. Baron; J.P. Sutter; Yoshitaka Yoda; H. Onodera; Daisuke Kikuchi; H. Sugawara; Hideyuki Sato; Chihiro Sekine; Ichimin Shirotani
Applied Physics A | 2002
Kenji Ohoyama; Koji Kaneko; Kentaro Indoh; Aya Tobo; H. Onodera; Y. Yamaguchi