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  • 11
    Electronic Resource
    Electronic Resource
    Magnetization reversal in Co/Cr multilayer films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6353-6355 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization reversal of Co/Cr multilayer films is studied by utilizing initial magnetization curves, minor loops, isothermal and dc demagnetization remanence curves, and temperature dependence of the loops. Electron microscope observations reveal that the films consist of columnar grains of size from 400 to 800 A(ring). It is suggested that the magnetization reversal is dominated by rotation of single-domain grains. Numerical calculations are performed based on the Stoner–Wohlfarth coherent rotation model for noninteracting, single-domain particles of uniaxial anisotropy. The calculated results agree qualitatively with the experimental results. To investigate the quantitative differences, magnetic interactions among the grains are measured in terms of deviations from the linear Hankel plot predicted by Wohlfarth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352646
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  • 12
    Electronic Resource
    Electronic Resource
    Barrier height temperature dependence of Au/InP from photoreflectance spectroscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3447-3450 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The barrier height of Au/InP was measured at various temperatures from Franz–Kelydsh oscillations (FKO) of photoreflectance spectroscopy. It appears that the photoinduced voltage can not be neglected especially at low temperature. The presently observed barrier height temperature dependence confirms the theory of Hecht [M. Hecht, Phys. Rev. B 41, 7918 (1990)]. Also, the mixture between FKO and E0+Δ0 oscillations was observed. The degree of mixture varies with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355291
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  • 13
    Electronic Resource
    Electronic Resource
    Magnetic and structural properties of CoCrTa films and multilayers with Cr (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4710-4712 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report our studies of epitaxial growth of CoCrTa films on Cr underlayers and the properties of CoCrTa/Cr multilayers. The coercivity, Hc, strongly depends on Ta composition, sputtering conditions, and the thicknesses of the magnetic layer and Cr underlayer. An Hc value of 1300 Oe was obtained for a Ta composition of 2 at. %, a Cr underlayer thickness of 4000 A(ring), and a magnetic layer thickness of 400 A(ring). The x-ray data show that the high Hc occurs when crystallites of the Cr underlayer and CoCrTa layer are aligned with the Cr (200) and CoCrTa (110) planes in the film plane. Thus, the c axis of the CoCrTa lies essentially in the plane of the film. When the thickness of the magnetic layer increases above 1000 A(ring) the c axis begins to tip out of the film plane. The basal plane lattice parameter varies roughly linearly with Ta content up to 13 at. %. For the CoCrTa/Cr multilayered films, Hc values up to 1200 Oe were obtained although the c-axis orientation of the magnetic layer becomes somewhat dispersed. Models for the dependence of magnetization reversal on microstructure are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344808
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  • 14
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance study of Cu(II) in the Cu(II) doped (NH4)2[Zn(NH3)2(CrO4)2] and (NH4)2[Cd(NH3)2(CrO4)2]: Orientational disorder of NH3 and dynamically induced structural change (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3897-3904 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron paramagnetic resonance (EPR) spectra recorded at X band on Cu(II) in the Cu(II) doped single crystals of (NH4)2[Zn(NH3)2(CrO4)2] and (NH4)2[Cd(NH3)2(CrO4)2] showed an unusual temperature dependence in the temperature range between 4.2 and 370 K. This unusual temperature dependence is attributed to the dynamics of NH3 molecules. It is concluded that NH3 undergoes an order–disorder transition. This transition occurs at 282±2 K (T*) for (NH4)2[Zn(NH3)2(CrO4)2] and at 300±5 K for (NH4)2[Cd(NH3)2(CrO4)2]. For temperatures above T* the EPR spectra are found independent of temperature. This observation indicates that the NH3 molecules behave as free rotors rotating about their threefold symmetry axis. As the temperature is lowered, the free rotation gradually becomes hindered which leads at T* to site doubling in the EPR spectra. The hindered rotation simultaneously induces a structural change at T* reducing the local symmetry at the Cu(II) site from C2/m to approximately Cs. In the temperature range between T* and about 80 K, the EPR spectra with the magnetic field perpendicular to the threefold axis of NH3 are temperature dependent, but those with the magnetic field parallel to the threefold axis remain unchanged. This behavior is qualitatively interpreted as being due to the torsional oscillation of NH3. At temperatures lower than 80 K, the NH3 molecules exhibit the torsional oscillation of the lowest state and accordingly, all the EPR spectra become temperature independent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462928
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  • 15
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance, electron nuclear double resonance, and electron spin echo envelope modulation of Fe(CN)3−6 in a KCl lattice (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4698-4707 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and electron spin echo envelope modulation (ESEEM) study has been carried out on Fe(CN)3−6 in a KCl lattice. The EPR spectrum showed the formation of a large number of centers, which correspond to different configurations of the charge compensating cation vacancies. The two major centers called center Ia and Ib have been well characterized. Both centers have orthorhombic symmetry and show a large g anisotropy. The principle g values are: gx =2.079, gy =3.054, and gz =0.400 for center Ia; gx =2.007, gy =3.177, and gz =0.752 for center Ib. The ligand field splitting and the orbital reduction factor k have been obtained through analyzing the spectra in terms of the generalized spin Hamiltonian. A number of unusual features observed in the EPR spectra have been found to be due to the high level of g anisotropy. The ENDOR and ESEEM measurements performed on center Ia revealed nearly all the coupling tensors between the unpaired electron and the 13C and 14N nuclei. The principle values and tensor orientations were precisely determined by least-squares fitting. The orientations of the coupling tensors give a detailed picture of the complex under the influence of the two cation vacancies. The coupling constants of 13C were found to be an order of magnitude larger than those of 14N. Level anticrossing was observed for the nuclear spin states of 14N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457738
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  • 16
    Electronic Resource
    Electronic Resource
    Evaluation of modulating field of photoreflectance of surface-intrinsic-n+ type doped GaAs by using photoinduced voltage (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4101-4104 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) of surface-intrinsic-n+ type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz–Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field Fbi. In the previous work we have obtained the relation F(approximate)Fbi−δF/2 when δF(very-much-less-than)Fbi by using electroreflectance to simulate PR, where δF is the modulating field of the pump beam. In this work a method was devised to evaluate δF by using photoinduced voltages Vs and, hence, the relation can be verified by PR itself. The δFs obtained by Vs are also consistent with those of using imaginary part of fast Fourier transform of PR spectra. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1453492
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  • 17
    Electronic Resource
    Electronic Resource
    Effects of polarization on electroreflectance spectroscopy of surface-intrinsic n+-type doped GaAs (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 78-80 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electroreflectance (ER) spectra of a surface-intrinsic n+-type doped (100) GaAs have been measured at various polarization angles of the probe beam. Several Franz–Keldysh oscillations were observed above the band-gap energy, thus enabling heavy- and light-hole transitions to be separated by the application of the fast Fourier transform to the ER spectra. From this, the ratios of the amplitudes of the light- to heavy-hole transitions versus angle of polarization were obtained. At a large incident angle (80°), the strength of the field of the probe beam in the normal direction of the sample (Fz) was varied from zero to a larger component. It was found that the ratios increased with increasing Fz which is consistent with the theory that the light-hole transition becomes more enhanced with z-polarized light. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1420763
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  • 18
    Electronic Resource
    Electronic Resource
    Structure and magnetic properties of melt-spinning Pr(Fe0.6Co0.4)2 alloys (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6289-6291 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pr(Fe0.6Co0.4)2 ribbons were prepared by melt spinning with different wheel speeds from 35 to 45 m/s. Their structure, magnetic properties, and thermal stability are investigated. At a wheel speed of 35 m/s, the ribbon consists of a mixture of Pr(Fe,Co)2 cubic Laves phase and some noncubic phases. An almost Pr(Fe,Co)2 nanocrystalline single phase with a Curie temperature of 305 °C is obtained at a wheel speed of 40 m/s. Except for Pr(FeCo)2 phase a small amount of amorphous phase is observed with increasing wheel speeds to 45 m/s. Pr(Fe,Co)2 phase becomes unstable and decomposes above 770 °C. The resin-bonded Pr(Fe,Co)2 nanocrystalline phase which is obtained at a wheel speed of 40 m/s combines high magnetostriction (λ(parallel)−λ⊥=140 ppm), with significant coercivity, iHc=5 kOe. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372682
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  • 19
    Electronic Resource
    Electronic Resource
    Spin dependent tunneling devices fabricated for magnetic random access memory applications using latching mode (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6385-6387 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin dependent tunneling (SDT) devices were fabricated as building blocks for magnetic random access memory (MRAM) applications using latching electronics. The basic SDT structure was NiFeCo/Al2O3/CoFe/IrMn deposited using rf diode sputtering. The SDT structures and the word and torque coils were patterned using standard photolithography techniques. The junction magnetoresistance was 25.6%, the switching field was 12 Oe, the junction resistance-area product was 116 kΩ μm2, and the pinning field was 150 Oe. There were two legs of SDT resistors in a latch cell, with each leg consisting of at least one pair of junctions. The basic latching function of the devices was evaluated using external electronics. The two memory states per cell were demonstrated by passing a current of 22 mA with both polarities through the on-chip word coil. This translates to a field efficiency of about 1 Oe/mA for the word coil, which can be further improved by adding a magnetic keeper layer. The raw output voltage change was 21 mV for a SDT cell with four junctions and 4.5 kΩ resistance in each leg using a 50 μA sense current. These results show great potential for SDT materials to be used in high speed and low power MRAM applications with latching mode. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372714
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  • 20
    Electronic Resource
    Electronic Resource
    Whistler turbulence at the magnetopause: A nonlinear generation mechanism (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 272-276 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma maser effect in the existence of enhanced kinetic Alfvén wave turbulence is investigated as the generation mechanism of the whistler turbulence at the magnetopause. The numerical results of the growth rate show that on the scale of neither the ion inertial length nor the electron inertial length, the whistler waves can be excited, and the peak of the maximum growth rate occurs on the scale of the effective ion Larmor radius. The kinetic Alfvén wave dynamics associated with the scale length of the effective ion Larmor radius is intrinsically important in the magnetic reconnection and leads to the generation of whistler turbulence. The theoretical model of the generation of whistler turbulence is useful for explaining the observations of intense electromagnetic fluctuations at the magnetopause. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326063
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