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1

Digitale Medien

Neutron diffraction study of lattice changes in Nd2Fe17−xSix(Cy) (1995)

Yelon, W. B. ; Hu, Z. ; Singleton, E. W. ; [weitere]

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

Journal of Applied Physics 78 (1995), S. 7196-7201

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Neutron diffraction has been used to determine the location and concentration of C in Nd2Fe17 and in a Si substituted alloy. The results indicate that two carbide phases exist. One contains nearly three C atoms per formula unit, while the other has a much lower concentration. The high C phase contains C only on the 9e sites, but the low C phase appears to contain C on the tetrahedral 18g site. The changes in interatomic distances and cell volume are associated with the different site occupancies. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.360726

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2

Digitale Medien

Phase transformation induced by gas phase reaction in RFe10SiCx alloys : 38th Annual Conference on Magnetism and Magnetic Materials (1994)

Singleton, E. W. ; Hadjipanayis, G. C. ; Papaefthymiou, V. ; [weitere]

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

Journal of Applied Physics 75 (1994), S. 6000-6002

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A new series of rare-earth iron intermetallic carbide compounds has been prepared by the reaction of powders with methane gas. The alloys prior to the methane heat treatment had the 2:17-type structure, R2(Fe,Si)17 (R=Y, Ce, Pr, Nd, and Sm). After heat treatment in temperatures up to 873 K the alloys absorb carbon and retain their original structure with a volume expansion over the carbon-free unit cell. For higher heat treatment temperatures (973–1073 K), a phase transformation occurs leading to the BaCd11-type structure. These compounds have a lower Curie temperature than those with the Th2Zn17-type structure, in the range of 453–495 K. Rietveld analysis of neutron diffraction data on NdFe10SiCx with the BaCd11-type structure are reported. In addition, the average hyperfine parameters determined by Mössbauer spectroscopy are reported for the Nd compounds.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.355488

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3

Digitale Medien

Mössbauer study of permanent-magnet R2Fe17−xMxCy compounds : The 40th annual conference on magnetism and magnetic materials (1996)

Al-Omari, I. A. ; Singleton, E. W. ; Zheng, Y. ; [weitere]

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

Journal of Applied Physics 79 (1996), S. 4590-4592

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We report Fe57 Mössbauer spectroscopy studies of the effect of carbon doping on the magnetic properties of the Fe sites of R2Fe17−xMxCy, and of the presence of multiple phases in these systems. In this study two systems, Sm2Fe14Al3Cy, where y=0, 1.0, 2.0, and 3.0, and Nd2Fe14.54Si2.46Cy, where y=0, 0.432, and 2.544, were measured at room temperature and analyzed. The ternary compounds R2Fe17−xMxCy studied here have the rhombohedral Th2Zn17 structure with c-axis anisotropy. The Al and Si site occupation used in the fitting were taken from previous results. Analysis of the Mössbauer spectra showed that the hyperfine fields for the different sites decreased in the order 6c, 9d, 18f, and 18h. The average hyperfine field for Sm2Fe14Al3Cy was found to increase with increasing carbon concentration, which is in qualitative agreement with magnetic measurements. For Nd2Fe14.54Si2.46Cy the average hyperfine field was found to increase for low C concentration and decrease for high C concentration; this behavior is in agreement with our magnetization measurements. The measured average isomer shift relative to α-iron was found to increase with y. In these compounds alloying with C and/or M can improve the magnetic properties such as Curie temperature and magnetization which make them potential candidates for permanent magnet development. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.361736

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4

Digitale Medien

Magnetic hardening of melt-spun nanocomposite Nd2Fe14B/Fe magnets : The 40th annual conference on magnetism and magnetic materials (1996)

Panagiotopoulos, I. ; Withanawasam, L. ; Murthy, A. S. ; [weitere]

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

Journal of Applied Physics 79 (1996), S. 4827-4829

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Coercivity optimization studies were done on melt-spun nanocomposite Nd4R2Fe87−xNbTxB6 (R=Nd,Y,Dy; T=Ag,Cu) isotropic ribbon samples. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties [HC=3.9 kOe, (BH)max=10 MGOe] were obtained by annealing at 750–775 °C for a few minutes. Optimization by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted grain size for optimum coupling between the hard and the soft phase. With the annealing conditions used, Nd4Dy2Fe87NbB6 samples gave moderate coercivities and in Nd4Y2Fe87NbB6 samples the coercivity was reduced more than the expected reduction in the anisotropy field due to the presence of Y. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.361621

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5

Digitale Medien

Effects of Cr, CrV, and CrTi underlayers on magnetic, structural, and materials reliability properties of CoPt thin films (1999)

Singleton, E. W. ; Narayan, P. B.

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

Journal of Applied Physics 85 (1999), S. 5840-5842

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Co80Pt20 thin films on Cr, Cr80V20, or Cr90Ti10 underlayers were studied to improve the magnetic properties for permanent magnetic stabilization layer application in anistropic magnetoresistance/giant magnetoresistance devices. A significant improvement of nearly 15% in coercivity was achieved for CoPt films on CrTi underlayer, when compared to either Cr or CrV underlayer. X-ray diffraction pattern analysis showed that CrTi underlayer increased the intensity of CoPt (10.0) indicating enhanced crystallographic in-plane texture. With CrTi underlayer, CoPt coercivity increased linearly as Mrt was reduced from 4.3 to as low as 0.4 memu/cm2. The squareness and S* values started to drop sharply when the Mrt of CoPt film decreased to below 1.0 memu/cm2. In addition to 15% higher coercivity, another important property of CrTi/CoPt was that for CrTi underlayer thickness between 3 and 20 nm very little change in the coercivity, squareness, and S* of CoPt layer was observed. The CoPt films showed excellent corrosion resistance towards high humidity and good thermal stability up to 300 °C. The CoPt films with the underlayer of CrTi and CrV showed slightly less corrosion resistance towards industrial pollutants than those with no underlayer and Cr underlayer. © 1999 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.369934

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6

Digitale Medien

Magnetic viscosity studies in hard magnetic materials (1990)

Singleton, E. W. ; Hadjipanayis, G. C.

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

Journal of Applied Physics 67 (1990), S. 4759-4761

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The magnetic viscosity behavior has been studied in several hard magnets with different magnetization reversal mechanisms including barium ferrite powders, Cu-Mn-Al, ferrite magnets, Nd-Fe-B, and SmCo5, Sm2(Co,Fe,Cu,Zr)17. The measurements were made with a vibrating sample magnetometer for times up to 60 s and a SQUID magnetometer for longer times in the range of 60–2300 s. For most of the samples the magnetization was found to vary logarithmically with time. The field and temperature dependence of the magnetic viscosity coefficient S was studied. Here, S was found to vary with the applied field and it usually peaked around the coercive field Hc. The measured values of Smax at 10 K range from 0.004 to 1.853 emu/g for Cu-Mn-Al and Sm2(Co,Fe,Cu,Zr)17, respectively. The magnetic viscosity coefficient was used together with the magnetic susceptibility to determine the activation volume.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.344777

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7

Digitale Medien

Hard magnetic properties of melt-spun Nd(Fe,M)12 nitrides and carbides : 37th Annual conference on magnetism and magnetic materials (1993)

Tang, Z. X. ; Singleton, E. W. ; Hadjipanayis, G. C.

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

Journal of Applied Physics 73 (1993), S. 6254-6256

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The hard magnetic properties of melt-spun Nd(Fe,M)12 nitrides and carbides were studied. The highest coercivity was obtained in NdFe10Mo2Nx with values of 8.8 kOe at room temperature and 33.7 kOe at 10 K. Other Nd(Fe,M)12N(C)x compounds had similar intrinsic magnetic properties but a lower coercivity than NdFe10Mo2Nx. The low coercivities were attributed to the three soft sources; α-Fe, non-ThMn12 structure, and insufficient nitrogenation or carbonation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.352662

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8

Digitale Medien

Magnetic hardening in as-cast Nd-rich Nd-Fe-B magnets : 35th annual conference on magnetism and magnetic materials (1991)

Singleton, E. W. ; Tsoukatos, A. ; Zhang, Y. ; [weitere]

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

Journal of Applied Physics 69 (1991), S. 5820-5822

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The microstructure of as-cast Nd-rich Nd-Fe-B alloys has been studied in detail and correlated with their magnetic hysteresis behavior. A hard magnetic phase with a Curie temperature around 250 °C and a coercivity of 5.2 kOe has been observed in an arc-melted Nd80Fe15B5 sample. Annealing at around 600 °C led to a transformation of this phase to Nd2Fe14B which is present in the form of small crystallites randomly disbributed in a nonmagnetic Nd-rich matrix, resulting in coercivities greater than 14 kOe. The Stoner and Wohlfarth model of single domain particles has been used to discuss the large coercivities.〈lz〉 〈lz〉 〈lz〉 〈lz〉 〈lz〉 〈lz〉

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.347860

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9

Digitale Medien

Magnetic and structural properties of melt-spun rare-earth transition-metal intermetallics with ThMn12 structure (1988)

Singleton, E. W. ; Strzeszewski, J. ; Hadjipanayis, G. C. ; [weitere]

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

Journal of Applied Physics 64 (1988), S. 5717-5719

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The magnetic and structural properties of melt-spun R8Fe84Ti8 with R=Nd, Sm, Dy, Gd and R8(Fe,Co)76[V(Mo)]16 with R=Nd, Sm have been studied with x-ray diffraction, transmission electron microscopy, and magnetic measurements. The tetragonal ThMn12-type structure was found in all alloys after annealing at about 700 °C. The Curie temperature (Tc) of the as-spun amorphous samples was in the range of 40–100 °C. Crystallized Nd8(Fe1−xCox)84Ti8 samples with the 1:12 structure have a Tc around 250 °C for x=0, reaching the value of 660 °C for x=0.5 and then decreasing again to 490 °C for x=1. ac susceptibility studies on Co-substituted samples showed magnetic transitions in the temperature range 100–200 K. The coercivity was found to be strongly dependent on the microstructure. The highest value of Hc (2 kOe) was obtained in Sm-Fe-Ti samples with a grain size about 500 A(ring). The upper value of Hc is low because of the presence of some α-Fe in crystallized ribbons.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.342236

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10

Digitale Medien

Magnetic properties of rare-earth transition-metal borides (1988)

Aly, S. H. ; Singleton, E. ; Hadjipanayis, G. C. ; [weitere]

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

Journal of Applied Physics 63 (1988), S. 3704-3706

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The magnetic and structural properties of quaternary RCo4−xFexB alloys with R=Nd, Sm, Er have been examined with magnetometry and x-ray diffraction. The CeCo4B-type phase is found for all x in Er, for x≤3 in Sm, and for x=0, 1, and 2 in Nd. Maximum coercivities have been obtained in a crystallized SmFe2Co2B sample with Hc〉17 kOe at room temperature.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.340641

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