H. Kuwahara
Sophia University
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Featured researches published by H. Kuwahara.
Nature | 1997
A. Asamitsu; Y. Tomioka; H. Kuwahara; Yoshinori Tokura
Magnetoresistive devices (based on, for example, magnetic multilayers) exhibit large changes in electrical resistance in response to a magnetic field, which has led to dramatic improvements in the data density and reading speed of magnetic recording systems. Manganese oxides having a perovskite structure (the so-called manganites) can exhibit a magnetoresistive response that is many orders of magnitude larger than that found for other materials, and there is therefore hope that these compounds might similarly be exploited for recording applications. Here we show that the switching of resistive states in the manganites can be achieved not only by a magnetic field, but also by an electric field. For manganites of the form Pr1−xCaxMnO3, we find that an electrical current (and by implication a static electric field) triggers the collapse of the low-temperature, electrically insulating charge-ordered state to a metallic ferromagnetic state. We suggest that such a phenomenon could be exploited to pattern conducting ferromagnetic domains within an insulating antiferromagnetic matrix, and so provide a route for fabricating micrometre- or nanometre-scale electromagnets.
Science | 1995
H. Kuwahara; Y. Tomioka; A. Asamitsu; Yutaka Moritomo; Yoshinori Tokura
An electronic (metal-to-insulator) phase transition of the first order, which can be caused by an external magnetic field, was discovered in Nd1/2Sr1/2MnO3. A clear hysteresis was observed during the increase and decrease of an external magnetic field at a fixed temperature. The hysteretic field region was observed to depend critically on temperature and to drastically expand with a decrease of temperature, perhaps as a result of suppression of the effect of thermal fluctuations on the first-order phase transition. Although it has seldom been observed, this is thought to be a generic feature of the first-order phase transition at low temperatures near 0 kelvin.
Science | 1996
Tsuyoshi Kimura; Y. Tomioka; H. Kuwahara; A. Asamitsu; M. Tamura; Yoshinori Tokura
The current-perpendicular-to-plane magnetoresistance (CPP-MR) has been investigated for the layered manganite, La2−2xSr1+2xMn2O7 (x = 0.3), which is composed of the ferromagnetic-metallic MnO2 bilayers separated by nonmagnetic insulating block layers. The CPP-MR is extremely large (104 percent at 50 kilo-oersted) at temperatures near above the three-dimensional ordering temperature (Tc ≈ 90 kelvin) because of the field-induced coherent motion between planes of the spin-polarized electrons. Below Tc, the interplane magnetic domain boundary on the insulating block layer serves as the charge-transport barrier, but it can be removed by a low saturation field, which gives rise to the low-field tunneling MR as large as 240 percent.
Physical Review B | 1999
R. Kajimoto; Hideki Yoshizawa; H. Kawano; H. Kuwahara; Y. Tokura; Kenji Ohoyama; Masayoshi Ohashi
We have peformed neutron diffraction measurements on melt-grown polycrystalline samples of
Journal of the Physical Society of Japan | 1999
Yoshinori Konishi; Zhong Fang; Makoto Izumi; Takashi Manako; Masahiro Kasai; H. Kuwahara; Masashi Kawasaki; Kiyoyuki Terakura; Yoshinori Tokura
{\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}
Journal of Applied Physics | 1996
Y. Tokura; Y. Tomioka; H. Kuwahara; A. Asamitsu; Yutaka Moritomo; M. Kasai
Science | 1996
H. Kuwahara; Y. Tomioka; Yutaka Moritomo; A. Asamitsu; Masahiro Kasai; Reiji Kumai; Yoshinori Tokura
(0.49l~xl~0.75).
Applied Physics Letters | 1997
Y. Tomioka; H. Kuwahara; A. Asamitsu; M. Kasai; Yoshinori Tokura
A systematic transformation of the crystalline and magnetic structures of this system was observed. This can be consistently explained by the change of the character of the Mn
Journal of the Physical Society of Japan | 1997
Y. Tomioka; A. Asamitsu; H. Kuwahara; Yoshinori Tokura
{e}_{g}
Journal of Alloys and Compounds | 2001
Y. Tomioka; T. Okuda; Y. Okimoto; A. Asamitsu; H. Kuwahara; Yoshinori Tokura
orbitals. When increasing X, the
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National Institute of Advanced Industrial Science and Technology
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