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Digitale Medien

Effect of additive elements on magnetic properties and irreversible loss of hot-worked Nd-Fe-Co-B magnets : 35th annual conference on magnetism and magnetic materials (1991)

Yoshikawa, N. ; Kasai, Y. ; Watanabe, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 69 (1991), S. 6049-6051

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: There has been limited work on the effects of alloying elements on the properties of hot-worked anisotropic magnets. The coercivity mechanisms for sintered and rapidly solidified Nd-Fe-B magnets are different, and additives can have different effects on magnetic properties. The present study was conducted to clarify the effects of various alloying elements on the properties of hot-worked magnets. Ribbons of composition (Nd13.6−xRx)(Fe77.6−yTyCo2.8)B6.0 (R=Ce and Dy; T=Al, V, Cu, Ga, Zr, Nb, Mo, and Sn; x=0, 1, and 2; y=0, 0.5, and 1.0) were prepared by melt spinning. Anisotropic magnets were made at 1073 K with 55.6% reduction in height by die upsetting. Room-temperature magnetic properties and irreversible losses after exposure at 323–473 K were determined. The results showed that small amounts of Al, V, Cu, and Ga enhanced the remanence of the magnets, while Dy, Al, Ga, Zr, Nb, and Mo improved the coercivity. Dy, Ga, and Mo additions were effective in increasing the heat resistance temperature (HRT), defined as the temperature where the irreversible loss is 3%. HRT is dependent on initial intrinsic coercivity and the squareness ratio (Hk/iHc) of the demagnetization curve. An equation relating these parameters is given. An HRT of 453 K was obtained with a suitable alloy composition.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.347766

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Digitale Medien

Effect of additives on hot deformation behavior of melt-spun Nd-Fe-Co-B magnets : The 5th Joint MMM−Intermag Conference (1991)

Yoshida, Y. ; Yoshikawa, N. ; Nishio, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 70 (1991), S. 6363-6365

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The effect of various additives on hot workability was investigated for alloy systems of (Nd13.6−xRx)(Fe77.6−yTyCo2.8)B6.0: R=Ce, Dy; x=0, 1, 2; T=Al, Si, V, Cu, Ga, Zr, Nb, Mo, Sn; y=0, 0.5, 1.0. A semiquantitative comparison of the effect of various additives was made by measuring the crack opening displacement (CODmax) in test specimens deformed in an open (unconstrained) configuration. Among the additives, cerium and silicon improved the hot workability while niobium and tin severely deteriorated the workability. The remanence anisotropy ratio was inversely related to CODmax. Detailed microstructural investigations were carried out with alloys which had only cerium or tin to study the reason for their hot workability behavior in comparison to the base alloy. The improved hot workability of cerium added alloy is related to the lower melting temperature of the intergranular phase and faster grain growth compared to the base alloy. Tin addition prevented grain growth with no endothermic peak in a differential thermal analysis curve, indicating the absence of boundary phase melting, and leading to poor hot workability.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.349943

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Digitale Medien

Hot workability of melt-spun Nd-Fe-Co-B magnets : 35TH ANNUAL CONFERENCE ON MAGNETISM AND MAGNETIC MATERIALS San Diego, California (USA) 29 Oct−1 Nov 1990 (1991)

Yoshida, Y. ; Kasai, Y. ; Watanabe, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 69 (1991), S. 5841-5843

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Anisotropic Nd-Fe-B magnets are produced from melt-spun ribbons by hot working technique. The processing is facilitated by improved workability. In order to obtain a sound magnet, it is important to suppress the crack initiation and growth. An investigation was carried out to study the deformation mechanism of the alloy system and to improve workability by changes in alloy composition. Alloy ribbons with composition (Nd13.6−xRx) (Fe77.6−y Ty Co2.8)B6.0 [R=Ce, Dy; T=Al, Si, V, Cu, Ga, Zr, Nb, Mo, Sn; x= 0, 1, 2; y=0, 0.5, 1.0] were prepared by melt spinning and then hot pressed into fully dense compacts. These compacts were upset in a hot working simulator. Hot workability was evaluated by measuring the crack opening displacement on the surface at the half height of the upset specimen. The relationship between strain rate and flow stress was found to be expressed by the equation: ε(overdot) = Aσn exp( − Q/RT). Values of n and Q were obtained for quarternary composition (Nd-Fe-Co-B). The effects of strain and strain rate on magnetic properties were also studied for quarternary composition. Of the additive elements, cerium and silicon addition showed significant improvement in workability without loss of coercivity.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.347844

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Digitale Medien

Effect of additives on thermal stability of Nd-Fe-B bonded magnets (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)

Nishio, T. ; Yagi, H. ; Furuya, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 75 (1994), S. 6658-6658

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Effects of Zr and Nb on magnetic properties and thermal stability were studied for Nd-Fe-B bonded magnets. Bonded magnets with a composition of Ndx(Fe94-x-y)B6Ty, where T=Zr and Nb; x=11.0, 11.5, and 12.0; y=0, 0.5, 1.0, 1.5, and 2.0; were prepared by using melt spun ribbons. The addition of Zr up to 0.5 at .% increased the (BH)max of the bonded magnets, and further addition of Zr decreased the (BH)max at each Nd content level. Hci increased monotonously with an increase in Zr. (BH)max and Hci of the Nb containing bonded magnets also showed similar behavior. Irreversible flux loss after exposure at 180 °C for 1000 h significantly reduced with an increase in the Zr content at each Nd content level. Both the structural flux loss and the thermal fluctuation flux loss were reduced with an increase in the Zr content. An irreversible flux loss of about 5% was obtained when the Nd and Zr content were 11.5 at .% and 2.0 at. %, respectively. A similar value of irreversible flux loss was also obtained in Nb containing bonded magnets with the same composition. It was found that the oxygen pickup by the bonded magnets during the heat resistant test was well correlated to the structural loss of the bonded magnets. A structural flux loss of less than 3% was obtained when the oxygen pickup was less than 0.4 wt. % for both additives. SEM studies revealed that the grain size of the 2-14-1 phase observed in the additive-containing specimens was finer than that of the base alloy.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.356886

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Digitale Medien

Low rare-earth Nd–Fe–B bonded magnets with improved irreversible flux loss : The 41st annual conference on magnetism and magnetic materials (1997)

Nishio, T. ; Koyama, S. ; Kasai, Y.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 81 (1997), S. 4447-4449

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The effects of Nb addition on magnetic properties and irreversible flux loss were studied on bonded magnets with compositions of Nd8Fe86−xB6Nbx, where x=0–3. An irreversible flux loss was measured at Pc=2 after exposure at 393 K for 3.6 ks in air. It was found that the Nb addition of 2 at. % or more decreased the irreversible flux loss. The value was less than 5%, similar to that obtained with MQP-B magnets. Br decreased with the increase in Nb content. The effect of Nd content on the magnetic properties and irreversible flux loss was also studied on the bonded magnets with compositions of NdxFe92−xB6Nb2, where x=6–8. The bonded magnet with the optimum composition of Nd6.5Fe85.5B6Nb2 had Br similar to that of MQP-Q magnets that did not contain Nb, and the value of irreversible flux loss was comparable to that of MQP-B magnets. A multipole magnetizability test on the bonded magnets with the above optimum composition was carried out, and the total flux of the bonded magnets was about 10% higher than that of MQP-B magnets for the 23 mm outside diameter magnet with 48 poles. © 1997 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.364971

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6

Digitale Medien

Superconducting photorelaxation spectroscopy (1988)

Iguchi, I. ; Kasai, Y. ; Mochiku, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 63 (1988), S. 1714-1721

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A novel technique termed superconducting photorelaxation spectroscopy is described in detail which utilizes a superconducting tunnel junction for detection of phonons from optically illuminated semiconductors. The method makes use of a lock-in, highly sensitive, detection technique which allows for direct detection of phonons. The system noise is suppressed to the level of 100 pV, enabling one to detect the phonon signal with an S/N ratio of 104. It is demonstrated that the phonon signal detected does not depend upon the chopper frequency, in contrast to conventional photoacoustic spectroscopy. The phonon signal as a function of wavelength of light employing a silver optical reflector yields a clear band-gap structure and modulated structures in the deep-level region consistent with the measurements obtained by other techniques for GaAs and InP wafers. The model for the phonon-detection system with its associated sensitivity is presented. It appears this method will be a very promising technique to study the nonradiative states of semiconductor crystals.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.339907

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Large magnetoresistance in Heusler-alloy-based epitaxial magnetic junctions with semiconducting Cu(In0.8Ga0.2)Se2 spacer (2016)

S. Kasai, Y. K. Takahashi, P.-H. Cheng, Ikhtiar, T. Ohkubo, K. Kondou, Y. Otani, S. Mitani and K. Hono

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publikationsdatum: 2016-07-23

Beschreibung: We investigated the structure and magneto-transport properties of magnetic junctions using a Co 2 Fe(Ga 0.5 Ge 0.5 ) Heusler alloy as ferromagnetic electrodes and a Cu(In 0.8 Ga 0.2 )Se 2 (CIGS) semiconductor as spacers. Owing to the semiconducting nature of the CIGS spacer, large magnetoresistance (MR) ratios of 40% at room temperature and 100% at 8 K were obtained for low resistance-area product ( RA ) values between 0.3 and 3 Ω μ m 2 . Transmission electron microscopy observations confirmed the fully epitaxial growth of the chalcopyrite CIGS layer, and the temperature dependence of RA indicated that the large MR was due to spin dependent tunneling.

Print ISSN: 0003-6951

Digitale ISSN: 1077-3118

Thema: Physik

Publiziert von American Institute of Physics (AIP)

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Temperature dependence of magneto-transport properties in Co2Fe(Ga0.5Ge0.5)/Cu lateral spin valves (2016)

Ikhtiar, S. Kasai, Y. K. Takahashi, T. Furubayashi, S. Mitani and K. Hono

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publikationsdatum: 2016-02-09

Beschreibung: The non-local spin signals of Co 2 Fe(Ga 0.5 Ge 0.5 )/Cu lateral spin valves with sub-micron size dimensions were measured with varying temperatures. The non-local spin signal reaches 54 mΩ at 4 K, while it degrades down to 13 mΩ at room temperature. Analysis based on the one-dimensional spin diffusion model clarifies the dominant source for degrading of the spin signal is suppression of the spin diffusion length in Cu, not the spin polarization, indicating Co 2 Fe(Ga 0.5 Ge 0.5 ) keeps half-metallic nature even at room temperature. The temperature dependence of non-local spin signal was found to exhibit a downturn at 36 K. The presence of magnetic impurities, detrimental effect of which becomes more pronounced for diffusive transport in long Cu wires, is suggested to cause the observed downturn in non-local spin signals.

Print ISSN: 0003-6951

Digitale ISSN: 1077-3118

Thema: Physik

Publiziert von American Institute of Physics (AIP)

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Solving non-LTE problems in rotational transitions using the Gauss–Seidel method and its implementation in the Atmospheric Radiative Transfer Simulator (2018)

Yamada, T. ; Rezac, L. ; Larsson, R. ; [weitere]

EDP Sciences

In: Astronomy and Astrophysics. 2018; 619: A181. Published 2018 Nov 01. doi: 10.1051/0004-6361/201833566.

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Publikationsdatum: 2018-11-01

Beschreibung: This article presents our implementation of a non-LTE solver in spherical symmetry for molecular rotational transition in static or expanding atmospheres. The new open-source code relies on the Gauss–Seidel Accelerated Lambda Iteration methodology that provides a rapid and accurate convergence of the non-LTE problems, which is now routinely used in astrophysical and planetary research. The non-LTE code is interfaced with the widely used package, the Atmospheric Radiative Transfer Simulator (ARTS), to facilitate spectral line simulations for various viewing geometries. In this paper we describe the numerical implementation, provide the first validation results for the populations against two other non-LTE codes, and then discuss the possible application. The quantitative comparisons are performed using an established ortho-water non-LTE model applied to cases of optical thick and thin conditions of Ganymede’s atmosphere. The differences in populations expressed as excitation temperatures show very good agreement in both cases. Finally, we also apply this model to a sample of data from the Microwave Instrument for the Rosetta Orbiter (MIRO) instrument. The new non-LTE package is demonstrated to be fast and accurate, and we hope that it will be a useful addition to the planetary community. In addition, being open source and part of the ARTS, it will be further improved and developed.

Print ISSN: 0004-6361

Digitale ISSN: 1432-0746

Thema: Physik

Publiziert von EDP Sciences

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