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  • 1
    Electronic Resource
    Electronic Resource
    The origin of hard magnetic properties in rapidly quenched Nd4Fe77.5B18.5 alloy : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6980-6982 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Until now, the origin of hard magnetic properties of rapidly quenched Nd-Fe-B alloys with lower Nd concentration is not clear. In this paper, the phase compositions of rapidly quenched Nd4Fe77.5B18.5 alloys annealed under different conditions have been studied by using zero-field spin-echo nuclear magnetic resonance (NMR) and Mössbauer effect (ME) techniques. It is found that there exists a certain amount of Nd2Fe14B phase in the samples annealed at 960 °C and ingot alloy, which have poor hard magnetic properties; while, the sample annealed under optimal condition consists only of bct-Fe3B as the main phase and a small amount of a-Fe. However, the ME result indicates that about 5 at. % Fe atoms in FeIII (8 g) site of bct-Fe3B have been replaced by Nd atoms; the NMR result demonstrates that 11B NMR spectrum is the characteristic peak of bct-Fe3B, but it broadens asymmetrically to the high frequency side, which is due to the bct-Fe3B influenced by Nd atoms. The amplitude of radio frequency (rf) excitation field required to get the maximum 11B spin-echo signal from bct-Fe3B in the sample annealed at 839 °C is only about one third as much as that required to excite the 11B in the bct-Fe3B influenced by Nd atoms in the sample annealed at 670 °C for a short time, which implies the latter has a larger coercivity field than the former. It is concluded that the origin of hard magnetic properties of Nd4Fe77.5B18.5 alloy is not related to the 2:14:1 phase, but to the change of bct-Fe3B itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352404
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  • 2
    Electronic Resource
    Electronic Resource
    NMR study of the short range order in Fe–B amorphous powders prepared by borohydride reduction : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6983-6985 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Fe–B amorphous alloys powders with high boron concentration can be prepared by borohydride reduction (BHR). By adjusting technological factors, the Fe100−xBx amorphous powders with compositions ranging from x=17 to 40 can be easily obtained, but it is difficult to make the amorphous ribbons with such a high B concentration by using rapidly quenched technique, which can usually obtain the amorphous ribbons with the compositions ranging from x=12 to 25. Up to now, there are different points of view about if the short range order (SRO) in the Fe–B amorphous powders prepared by the BHR around room temperature is the same with that in the amorphous ribbons made by rapidly quenched and vapor depositing techniques. In this paper, the SRO in Fe100−xBx amorphous powders with various boron concentration prepared by the BHR have been studied by the zero field spin echo nuclear magnetic resonance (NMR) technique. It was shown that the types of SRO in these samples vary with the B concentration. There exist Fe3B- and Fe2B-like SRO and a small amount of α-Fe in the samples with lower B concentration, while there are Fe3B- and FeB-like SRO in the alloys with higher B concentration. Fe3B-like SRO, however, only exists in the amorphous ribbons obtained by rapidly quenched method. It can be concluded that there are different types of SRO in the amorphous alloys prepared by different methods. This conclusion can explain the reason why the average hyperfine field at Fe sites deceases with the B concentration increasing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352405
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  • 3
    Electronic Resource
    Electronic Resource
    Ion beam sputtered spin-valve films with improved giant magnetoresistance response (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4454-4456 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A large value of giant magnetoresistance ΔR/R=9% with an exchange field Hex=350 Oe has been measured from simple NiFe/CoFe/Cu/CoFe/IrMn top spin-valve films prepared by ion beam deposition (IBD) techniques. The exchange biasing was greatly enhanced when a synthetic pinned layer, CoFe/Ru/CoFe, is used in the spin-valve structures. Apparent exchange field values in excess of 2000 Oe and ΔR/R values above 8% have been obtained in synthetic spin-valve films. These IBD spin-valve films show excellent thermal stability and they are suitable for the applications in high density magnetic recording heads. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370372
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  • 4
    Electronic Resource
    Electronic Resource
    Exchange biasing and thermal stability of CoFe/PtPdMn films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4915-4917 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two sets of PtPdMn exchange biased films Ta 50 Å/CoFe 100 Å/PtPdMn (tAF) Å/Ta 50 Å, with PtPdMn thickness, tAF=350, 600 Å, were deposited on Si substrates by dc magnetron sputtering techniques. After magnetic annealing, these two sets of films exhibited values of exchange bias field, Hex=229 and 254 Oe, respectively. The PtPdMn layer was then thinned to various thicknesses from 600 down to 50 Å by ion beam etching. Hex does not retain its original value. It decreases with decreasing tAF and becomes zero at tAF∼75 Å. In addition, we have observed that the training effect or the anomalous hysteresis loss becomes more pronounced with decreasing tAF. This confirms that not only face-centered-tetragonal phase but, more critically, tAF plays role in determining exchange biasing and its thermal stability. The blocking temperature, TB, appears unaffected by the thinning of the PtPdMn layer, and no apparent change occurs in the local blocking temperature distribution, as suggested by the finite size effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373201
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic properties of ultrathin NiFe and CoFe films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6618-6620 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report the magnetic properties of ultrathin (15–200 Å) NiFe and CoFe films deposited using ion beam deposition techniques. They are symmetrically sandwiched between Ta, Cu, or Ta/Cu under and capping layers. NiFe and CoFe films grown between Ta/Cu and Cu/Ta bilayers exhibit the smallest magnetic thickness loss of about 1 Å. This interfacial magnetic dead layer thickness, t0, is about 5 Å for Cu-sandwiched films and about 15 Å for Ta-sandwiched films. As the film thickness becomes thinner than 100 Å, the magnetic properties are found to be more sensitive to the choice of material and growth environment. CoFe films show an interfacial contribution, λi, about ten times larger than that for NiFe films. Among others, NiFe and CoFe films sandwiched by Ta/Cu and Cu/Ta bilayers exhibit the smallest values of λi. The magnetic anisotropy in Ta-sandwiched CoFe films appears to be predominantly magnetoelastic in nature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372789
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of ion beam and magnetron sputtered thin Ta/NiFe films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5780-5782 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin Ta/NiFe films were deposited using ion beam deposition (IBD), pulsed, and static magnetron sputtering techniques. These NiFe films show anisotropy field values ∼4 Oe, easy axis coercivities ≤1 Oe, and hard axis coercivities ≤0.3 Oe. IBD films exhibit higher magnetoresistance ratios (ΔR/R), while little difference is noted between different deposition techniques in the sheet resistance of NiFe films. A ΔR/R value of 1.8% has been measured for a 90 Å IBD NiFe films. X-ray diffraction measurements indicate that NiFe films of the same thickness have about the same grain size regardless of deposition technique, however, IBD films exhibit superior (111) texture and crystallinity. Our results clearly indicate that the superior magnetic properties of thin IBD Ta/NiFe films are a result of high crystallographic quality of these films. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370124
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic properties of ion beam deposited CoCrPt hard bias films for magnetoresistive heads (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5843-5845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion beam deposition techniques have been employed to prepare Cr/CoCrPt bilayers for hard bias applications in giant/anisotropic magnetoresistive recording heads. The bilayers were deposited at different deposition angles, which is defined as the angle between deposition beam direction and substrate plane. The magnetic properties of CoCrPt films, such as coercivity (Hc), remnant magnetization–thickness product (Mrt), and coercive squareness (S*) as a function of CoCrPt layer thickness and deposition angle have been studied and correlated to film microstructures. Typical values of Hc, Mrt, and S* for a Cr100 Å/CoCrPt490 Å bilayer deposited at 42° are 1580 Oe, 2.90 memu/cm2, and 0.90, respectively. The increase in Mrt with increasing CoCrPt layer thickness at a fixed deposition angle is accompanied by a linear decrease in Hc. We have observed, however, that for the same bilayer geometry both Hc and Mrt of CoCrPt layer increase with decreasing deposition angle, whereas S* remains almost unchanged. High angle x-ray diffraction measurements indicate that the hexagonal-close-packed (101¯0) crystallographic orientation of CoCrPt films is enhanced with decreasing deposition angles. This suggests that the improvement in both Mrt and Hc for CoCrPt films deposited with decreasing deposition angle results from an enhancement in in-plane c-axis texture, and crystallinity. This could be attributed to an enhancement in in-plane adatom mobility at low deposition angles. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369935
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of base pressure on FeMn exchange biased spin-valve films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4933-4935 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of base pressure, Pb, on physical properties of FeMn exchange biased spin-valve films was studied by varying Pb over two decades from 3×10−8 to 7×10−6 Torr. Giant magnetoresistive value shows a slight increase with increasing Pb until a large decrease occurs at Pb〉3.3×10−6 Torr. Exchange bias field and blocking temperature remain constant in the base pressure range between 3×10−8 and 5×10−7 Torr before a large reduction appears. Our results indicate an upper limit for base pressure, uPb(approximate)5×10−7 Torr, above which significant spin-valve performance modification and deterioration in the crystallographic texture begin as a result of the contamination both at the ferromagnetic/antiferromagnetic interface and in the bulk of FeMn layer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373207
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  • 9
    Electronic Resource
    Electronic Resource
    Generation of diamond nuclei on amorphous SiO2 by alternating-current bias microwave plasma chemical vapor deposition (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 16-18 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nucleation of diamond on the amorphous SiO2 mirror surface has been achieved by means of adding an ac signal to the negative dc bias in the microwave plasma chemical vapor deposition. It is found in experiment that the nucleation of diamond happens only after the frequency of the ac signal exceeds a threshold. The results also show that the diamond nucleation density depends not only on the ac frequency but also on the magnitudes of the ac signal and the dc bias. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114166
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  • 10
    Electronic Resource
    Electronic Resource
    Infrared vision using uncooled micro-optomechanical camera (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3567-3569 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This letter presents the design, fabrication, and imaging results of an uncooled infrared (IR) camera that contains a focal plane array of bimaterial microcantilever sensors, and an optical readout technique that measures cantilever deflections in the nanometer range to directly project a visible image of the IR scene on the human eye or a visible camera. The results suggest that objects at temperatures as low as 100 °C can be imaged with the best noise-equivalent temperature difference (NEΔT) in the range of 10 K. It is estimated that further improvements that are currently being pursued can improve NEΔT to about 50 mK. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124163
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