Kawazoe Frontier Technologies Co.

Yokohama-shi, Japan

Kawazoe Frontier Technologies Co.

Yokohama-shi, Japan
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Mizusaki S.,Aoyama Gakuin University | Naito M.,Aoyama Gakuin University | Taniguchi T.,Aoyama Gakuin University | Nagata Y.,Aoyama Gakuin University | And 5 more authors.
Journal of Physics Condensed Matter | Year: 2010

The variation of the magnetic moment on Ru and Mn atoms in the Ca 0.3Sr0.7Ru1-xMnxO3 system was investigated by the magnetic Compton scattering technique using synchrotron radiation. The Ca0.3Sr0.7Ru1-xMn xO3 system has ferrimagnetism with an antiferromagnetic coupling between Ru and Mn, and the dominant magnetic component changes from ferromagnetic Ru to ferromagnetic Mn at x ∼ 0.25 as the Mn substitution proceeds. The mechanism for the change in the magnetism of Ca 0.3Sr0.7Ru1-xMnxO3 is discussed. © 2010 IOP Publishing Ltd.


Mizusaki S.,Aoyama Gakuin University | Ohnishi T.,Aoyama Gakuin University | Douzono A.,Aoyama Gakuin University | Hirose M.,Aoyama Gakuin University | And 6 more authors.
Journal of Physics Condensed Matter | Year: 2012

The antiferromagnetism in Ru 2MnGe can be suppressed by the substitution of V by Mn and ferromagnetism appears. Synchrotron-based magnetic Compton scattering experiments are used in order to investigates the role of 3d electrons in the indirect/direct exchange interactions for the appearance of ferromagnetism. A small spin moment for the itinerant electron part on the magnetic Compton profile indicates that the metallic ferromagnet Ru 2Mn 0.5V 0.5Ge has a weak indirect exchange interaction between the d-like and sp-like (itinerant) electrons. This suggests that the appearance of ferromagnetism is caused by the enhancement of the direct exchange interactions between dd electrons in the Ru 2MnGe Heusler compound. These findings indicate that the indirect exchange interaction between itinerant electrons and localized electrons is a significant key point for the appearance of ferromagnetism in this system. © 2012 IOP Publishing Ltd.


Mizusaki S.,Aoyama Gakuin University | Ohnishi T.,Aoyama Gakuin University | Ozawa T.C.,Japan National Institute of Materials Science | Noro Y.,Kawazoe Frontier Technologies Co. | And 3 more authors.
Journal of Applied Physics | Year: 2012

The spin-polarized electron momentum density distributions (magnetic Compton profiles) of Co 2YAl (Y Ti, V, Cr, and Fe) Heusler compounds have been measured using a magnetic Compton scattering technique. The experimental magnetic Compton profiles have been decomposed into the itinerant electron and localized 3d electron contributions. The decomposition shows that the number of spin-polarized itinerant electrons is proportional to that of spin-polarized localized 3d electrons, indicating that the strength of indirect exchange interaction is dominated by the localized 3d magnetic moment. This finding suggests that the spin-polarized itinerant part in the magnetic Compton profile is used as a scale that can measure the strength of the sp-d interaction. © 2012 American Institute of Physics.


Mizusaki S.,Aoyama Gakuin University | Ohnishi T.,Aoyama Gakuin University | Ozawa T.C.,Japan National Institute of Materials Science | Noro Y.,Kawazoe Frontier Technologies Co. | And 4 more authors.
IEEE Transactions on Magnetics | Year: 2011

The magnetic properties of the polycrystalline Heusler compound Co 2TiAl were investigated by the classical experimental methods and the magnetic Compton scattering experiment. The X-ray diffraction profile at room temperature can be identified as the phase of the L21-type ordered structure. The magnetic field and temperature dependence of magnetization show that Co2TiAl has the typical soft ferromagnetic properties with TC of 120 K and the saturation magnetization of 0.70 μB per formula unit. The resistivity shows a typical metallic behavior at temperatures up to 300 K. The magnetoresistance (MR) effect with the MR ratio of - 8% appears in the vicinity of TC. The characteristics of the magnetic Compton profile are similar to that of the well-known ferromagnetic metals such as Ni and Fe. The experimental results indicate that the origin of the MR effect observed for Co2TiAl is similar to that for conventional ferromagnetic materials. © 2011 IEEE.


Mizusaki S.,Aoyama Gakuin University | Douzono A.,Aoyama Gakuin University | Ohnishi T.,Aoyama Gakuin University | Ozawa T.C.,Japan International Center for Materials Nanoarchitectonics | And 2 more authors.
Journal of Alloys and Compounds | Year: 2013

We report the composition-induced metal-insulator crossover transition in Ti substituted Ru-based metallic full Heusler alloy Ru2MnGe where the both end of materials shows a metallic properties. The samples at the middle composition show the large negative magnetoresistance effect. The experimental results of the resistivity and the magnetization indicate that this metal-insulator transition is induced by the Kondo effect because Ti atoms on antiferromagnetic Ru2MnGe have an important role in appearance of insulator states. © 2012 Elsevier B.V. All rights reserved.


Mizusaki S.,Aoyama Gakuin University | Douzono A.,Aoyama Gakuin University | Ohnishi T.,Aoyama Gakuin University | Ozawa T.C.,Japan International Center for Materials Nanoarchitectonics | And 3 more authors.
Journal of Alloys and Compounds | Year: 2012

The present study reveals that the correlation between the magnetic properties with composition x in the polycrystalline Ru2Mn 1-xFexGe system. Hard ferromagnetic properties appeared at the intermediate composition between antiferromagnetic Ru2MnGe with soft ferromagnetic Ru2FeGe. Ru2Mn0.6Fe 0.4Ge shows an anisotropic and negative magnetoresistance (MR) effect more than 8% although the both end materials are small MR effect less than 1%. These experimental results correlate the variation in MR ratio with that of coercive field as a function of x. Moreover, the correlation is shown at the boundary of magnetism between antiferromagnetic and ferromagnetic. Therefore, the present experimental results imply that the coexistence of antiferromagnetic and soft ferromagnetic leads to induce the MR effect in this system. © 2011 Elsevier B.V. All rights reserved.


Mizusaki S.,Aoyama Gakuin University | Douzono A.,Aoyama Gakuin University | Ohnishi T.,Aoyama Gakuin University | Nagata Y.,Aoyama Gakuin University | And 3 more authors.
Journal of Physics: Conference Series | Year: 2010

The crystallographic and magnetic properties of the quaternary Heusler alloys Ru2Mn1-xVxGe were investigated. Although the end members, Ru2MnGe (x = 0) and Ru2VGe (x = 1), are antiferromagnetic and paramagnetic, ferromagnetism with Curie temperature over 200 K appeared at about x = 0.3. The saturation magnetization had a maximum (1.6μB/f.u.) at x = 0.5. The ferromagnetism was explained by a model which assumes a preferential site occupation of V atoms and a collapsing of the next nearest-neighbor antiferromagnetic Mn-Mn interactions by V. © 2010 IOP Publishing Ltd.


Ohnishi T.,Aoyama Gakuin University | Taniguchi T.,Aoyama Gakuin University | Ikoshi A.,Aoyama Gakuin University | Mizusaki S.,Aoyama Gakuin University | And 8 more authors.
Journal of Alloys and Compounds | Year: 2010

The crystallographic and magnetic properties of perovskite-type rhodite LnRhO3 (Ln = rare-earth ions except Ce and Pm) were studied. LnRhO3 (Ln = La, Eu, Lu) shows paramagnetism with very small susceptibility, suggesting that the Rh3+ ion has no magnetic moment. LnRhO3 (Ln = Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb) shows antiferromagnetic transition at temperatures between 0.5 and 3.5 K; however, no transition was observed for LnRhO3 (Ln = Pr, Tm) down to 0.5 K. The effective moment μeff agrees with the theoretical moment of free rare-earth ions, indicating the dominant magnetic contribution of rare-earth ions. The Weiss temperature Θ has a strong correlation with the spin value of rare-earth ions, suggesting that the superexchange interaction is a dominant interaction in LnRhO3. The magnetization of antiferromagnetic samples tends to be saturated above 20-30 kOe, but the moments at 70 kOe are far from the theoretical moments. Antiferromagnetic samples seem to have an intermediate state and require a more intense magnetic field to attain saturation. © 2010 Elsevier B.V. All rights reserved.


Ohnishi T.,Aoyama Gakuin University | Naito M.,Aoyama Gakuin University | Mizusaki S.,Aoyama Gakuin University | Nagata Y.,Aoyama Gakuin University | Noro Y.,Kawazoe Frontier Technologies Co.
Journal of Electronic Materials | Year: 2011

The magnetic, transport, and thermoelectric properties of Ca 1-x Sr x Ru 1-y Mn y O 3 have been investigated. Ferromagnetism with relatively high T C (>200 K) was introduced by Mn doping. In particular, ferromagnetism appeared in the Ca 0.5Sr 0.5Ru 1-y Mn y O 3 system at y > 0.2. The maximum T C (=270 K) was recorded for a specimen of Ca 0.5Sr 0.5Ru 0.4Mn 0.6O 3. The ferromagnetism seems to be due to the mixed-valence states of Mn 3+, Mn 4+, Ru 4+, and Ru 5+ ions. The metallic character of Ru-rich specimens was suppressed by Mn substitution, and the system was transformed into a semiconductor at relatively low Mn content near y = 0.1. Specimens with higher Mn content (y > 0.8) had large thermoelectric power (50 μV K -1 to 130 μV K -1 at 280 K) accompanied by relatively low resistivity (0.03 Ω cm to 1 Ω cm). The Ca 0.5Sr 0.5Ru 1-y Mn y O 3 system seems to have good potential as a thermoelectric material for use above 300 K. © 2010 TMS.


Ohnishi T.,Aoyama Gakuin University | Seya K.,Aoyama Gakuin University | Higashino M.,Aoyama Gakuin University | Mizusaki S.,Aoyama Gakuin University | And 2 more authors.
IEEE Transactions on Magnetics | Year: 2011

Epitaxial layered films of CaMnO3 (CMO) and CaRuO3 (CRO) were fabricated on a SrTiO3(001) substrate by spin-coat method using organometallic solutions (metal alkoxides). Results of X-ray diffraction analysis and transmission electron microscopy indicate that the CaMO3 (M=Mn, Ru) films were deposited epitaxially so as to align the pseudocubic (00l) plane of CaMO3 perpendicular to the (001) plane of the SrTiO3 substrate. Ferromagnetism and metal-insulator transition were observed for the films with small CMO-layer thickness. The ferromagnetism was enhanced when the number of the interface between CMO and CRO layer was increased. The occurrence of ferromagnetism was explained assuming a mixed valence state of Ru and Mn ions and the double exchange interaction between Mn3+ and Mn4+ ions. © 2011 IEEE.

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