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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6244-6246 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of composition, annealing temperature, and annealing time on the magnetic properties and microstructure of Fe66M2Nd20C9.5B0.5 (M=Ga,Nb,Cu,Al) ingot magnets are presented. It has been found that the magnitude of the hard magnetic properties, which evolve during the solid-state transformation Fe17Nd2Cx to Fe14Nd2C, depends on the additive elements. These additions which decrease the melting temperature of the intergranular phase accelerate the transformation process and those which increase this temperature retard the transformation. Coercivities up to 880 kA/m combined with a remanence 0.58 T were produced in alloy ingots with Cu. The initial grain size was found to be crucial in producing good magnetic properties and coercivities as high as 980 kA/m were achieved for Fe-Nd-C-B alloy magnets hot pressed from microcrystalline melt spun ribbon. A modest increase of remanence (∼0.7 T) was achieved by die-upset forging of ingot alloys.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6116-6118 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanostructured ribbons in the compositional series Pr12(Fe100−xCox)82B6, x=0–30, having mean crystallite sizes dg in the range of 35–45 nm, were produced by overquenching and annealing. These had excellent second quadrant loop shapes and magnetic property combinations (iHc=390–785 kA/m, (BH)max=100–220 kJ m−3), equivalent to those obtained previously by direct quenching to the nanocrystalline state. In particular, these excellent combinations of properties were obtained without additions of a grain refining agent, such as Zr, which has been reported to be a requirement for obtaining good loop shapes and properties for overquenched and annealed ternary melt spun PrFeB alloys. An additional advantage of the Co substitution for Fe is enhanced Curie temperature. It was found, however, that for nanocomposite substoichiometric alloy ribbons (compositions in the series Pr10(Fe100−xCox)84B6, x=0–40) the second quadrant hysteresis loop shapes for overquenched and annealed ribbons were generally poor and, even though Jr was still substantially enhanced (in the range 0.95–1.05 T), the intrinsic coercivities iHc were disappointingly low (275–450 kA/m). Substitution of 1 at. % Zr for Fe in the Pr10Fe84B6 alloy, nevertheless, resulted in an improved loop shape and iHc (525–550 kA/m), with (BH)max increased to 130–140 kJ m−3 (compared with 80–110 kJ m−3 for the Zr-free alloys). © 2000 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3769-3774 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase evolution, microstructure, and magnetic properties of Nd8Fe86B6−xCx (x=0, 2, 4, 5, 6) melt-spun ribbons were systematically studied as a function of C content. It was found that the addition of C decreases the glass-forming tendency of the as-spun ribbons significantly. A uniform nanoscale exchange coupled Nd2Fe14(BC)/α-Fe microstructure with an average grain size of 20–25 nm can be developed in the directly quenched ribbons with C contents up to 4 at. %. Further increase of C content to x=5 leads to, in the optimally quenched ribbons, the presence of an undesirable Nd2Fe17Cx phase in addition to the 2:14:1 and α-Fe phases, whereas the alloy ribbon containing 6 at. % C consists almost entirely of the soft magnetic Nd2Fe17Cx and α-Fe phases. Subsequent annealing induces a transformation of the 2:17:Cx phase to the 2:14:1 phase +α-Fe in the ribbons with x=5 and 6, resulting in the formation of a composite 2:14:1/α-Fe structure having relatively large crystallite sizes. Magnetic measurements revealed that, for the optimally processed samples, replacement of up to 4 at. % of B by C significantly increases the coercivity iHc, with only slight reduction in remanence Jr; an optimum coercivity of 542 kA/m was obtained in the Nd8Fe86B2C4 ribbon compared with 430 kA/m for the Nd8Fe86B6 ribbon. Excessive substitution of C (x〉4) causes a drastic deterioration of both iHc and Jr due to the microstructural coarsening. Moreover, the Curie temperature of the 2:14:1 phase in the samples decreases progressively with increasing C content from 312 °C for x=0 to 270 °C for x=6. © 2002 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6473-6475 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ternary Fe82.4Nd13.1B4.5 alloy, which exhibits enhanced remanence (0.92 T) in the rapidly solidified state, was further modified by partial substitution of Nb or Si, or both Nb and Si, for Fe. The latter alloys containing Nb and Si, while maintaining remanence and coercivity values comparable with those obtained for ternary and quaternary compositions, exhibit higher (BH)max of ∼150 kJ m−3. This results from improved squareness of the demagnetization curve in the second quadrant of the B-H loop and is due to a more homogeneous distribution of very small (∼20–30 nm) crystallites through the ribbon thickness. This can be attributed to the effect of increased undercooling of the liquid alloys containing Nb and Si on quenching.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6366-6368 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of grain size on the magnetic properties of a rapidly solidified low boron Fe-Nd-B alloy, both in directly quenched and in the overquenched and annealed conditions, has been studied. The magnetic properties in the as-quenched crystalline state and changes occurring on annealing of the overquenched ribbons are discussed in relation to the microstructure. High values of the remanent magnetization, above 0.9 T (9 kG), in combination with coercivities of 1100 kA m−1 (13.7 kOe), have been observed for the directly quenched, isotropic single-phase ribbons, for certain combinations of process conditions. The mean-grain size for these ribbons measured on the roll contact side was found in some cases to be 〈20 nm, representing an essentially nanocrystalline structure. The enhanced remanence is considered to result from intergranular magnetic exchange interactions between fine adjacent grains. The overquenched ribbons were aged at temperatures between 500 and 800 °C for various times and these exhibited grain sizes in the range of 40–55 nm. Their magnetic properties depend on the annealing temperature and are generally lower than for the directly quenched ribbons though Br is still slightly enhanced at 0.85 T (8.5 kG). Apart from the effect of larger grains, the lower magnetic properties of the overquenched and annealed ribbons result from a slightly different phase constitution. Indirect evidence of this is provided by initial magnetization and coercivity measurements, using a VSM, which indicate that, on devitrification of the overquenched amorphous phase, a small proportion of soft magnetic phase was always present but which was not observed in the optimal directly quenched samples. Details of the phase transformations are discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5911-5913 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The initial results of a systematic study of the effects of Nd:Pr ratio and Fe:didymium (where didymium is a mixture of Nd and Pr) ratio on the magnetic properties of nanocrystalline melt spun didymium–Fe–B alloys are presented and discussed. The stoichiometric composition, corresponding to didymium2Fe14B, with Nd:Pr ratios of 1:3, 1:1, and 3:1 and the alloy series didymiumy Fe94−yB6, with y=8, 10, 12, and 14 at % were investigated. Enhancement of remanence and energy product was observed for all compositions studied, arising from intergrain exchange coupling between the RE2Fe14B crystallites (generally having a mean diameter ∼40 nm) and, for the off-stoichiometric alloys, also between the RE2Fe14B and α-Fe grains. An excellent combination of (BH)max(185 kJ m−3) and intrinsic coercivity (810 kA/m) was observed for the (Pr0.75Nd0.25)2Fe14B alloy. © 1999 American Institute of Physics.
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used an oriented single crystal of Nd2Fe14B1 as a test sample to explore contrast and resolution as a function of magnetic force microscopy tip coating, tip scan height, and sample history. We find that resolution is independent of tip type; that contrast is greater at low scan heights and for higher moment tips; and that the fine length scale structure of order 25 nm can be resolved. We further show how the surface structure is a function of state (demagnetized or remanent), demonstrating the ability of well-characterized studies to give high-resolution information on carefully prepared samples. © 1998 American Institute of Physics.
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Al on the magnetic properties of nanocrystalline Fe73.5−XAlXSi13.5B9Cu1Nb3 alloy ribbons, where 0≤X≤10, are reported for the first time. The evolution of the structure and magnetic properties of the ribbons, which were initially cast into the amorphous state in an inert gas environment at subatmospheric pressure, were studied as a function of annealing temperature Tann. The minimum dc coercivity developed during annealing, Hcmin, was found to decrease significantly with increasing Al content from 0.5 A/m at X=0 to 0.3 A/m at X=2 and to remain at approximately this level over the range 2〈X≤8 before rising to 0.4 A/m at X=10. The saturation polarization, Js, was, however, found to decrease linearly over this range from Js=1.5 T at X=0 to Js=0.9 T at X=10 for samples exhibiting Hcmin. As there was little significant reduction in the mean crystallite size, dg, at Hcmin with increasing X, this decrease in coercivity was considered to result from a reduction of the magnetocrystalline anisotropy, K1, of the crystallites as a result of the incorporation of Al. © 1998 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3184-3186 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural and magnetic properties of Fe73.5Si13.5B9Cu1Nb3 alloy wire and ribbon have been studied after thermal treatments up to temperatures at which partial (75%) devitrification to a nanocrystalline structure occurs. Nanocrystals are detected by x-ray diffraction only after treatments around 500 °C, while differential scanning calorimetry studies suggest that substantial structural change is inititiated at a much lower temperature (about 400°). A clear magnetic hardening is observed in samples heated within the temperature range 400–480 °C. This phenomenon is also accompanied by an increase of the linear magnetostriction. These effects are discussed in terms of the local structural rearrangements produced during the first stages of the crystallization process. The study is also extended partly to FeSiB, FeSiBCu, and FeSiBNb alloys.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 17 (1977), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of metribuzin and glyphosate at 100 ppm on carbon dioxide evolution and nitrogen transformation in two soils have been investigated in the laboratory. Both herbicides reduced CO2 evolution from Boddington Barn soil (organic carbon content 1.5%, pH 6.6) at some dates, but neither gave any consistent effects on Triangle soil (organic carbon content 4.0%, pH 5.1). Both metribuzin and glyphosate stimulated mineralization of nitrogen for at least 9 weeks. Only metribuzin on Triangle soil gave any indication of inhibition of nitrification. Metribuzin degraded more rapidly in Triangle soil than in Boddington Barn.
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