ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6504-6506 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A micromagnetic simulation program has been used to calculate the magnetoresistance of a free-standing 4 μm×1 μm×200 A(ring) Permalloy strip for a variety of numerical hysteresis loops in which a constant bias field is applied along the easy axis and a variable field is applied along the hard, in-plane axis. The main purpose of this study is to correlate noise in the magnetoresistive response with micromagnetic behavior and to show that the noise is considerably reduced by the application of the bias field. Two different methods for evaluating the magnetoresistive response are discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6528-6528 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In previous micromagnetic modeling1,2 of permalloy particles made by nanolithography,3 each individual particle is assumed to be a rectangular plate, but scanning electron micrographs show that the particles are better described by thin plates with round ends. Using our finite element code, we have investigated the effects of corner shapes of the permalloy particles. These particles are all 1.47 mm long, 0.18 mm wide, and 50 nm thick. The particle with semicircular ends has a higher coercivity and shows better agreement with the experiments than the particle with square ends. Qualitatively distinct behaviors are also found among interacting pairs of particles with different shapes at the ends. We have also studied the effects of voids. When the dimension of a void is much less than the exchange length of the material, the micromagnetics of the particle is not affected. For larger voids, particles with one, two, and three voids have been studied. Their easy axis hysteresis loops are all compared to the hysteresis loop of a voidless particle. It has been found that voids near the ends of the particle can serve as pinning sites and tend to increase the coercivity. On the other hand, a void in the middle of the particle reduces the coercivity because of an increase of the self demagnetizing field.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5276-5278 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization distributions in a rectangular permalloy particle with an 8:1 aspect ratio are presented. When a magnetic field is applied along the easy axis of the particle, there is considerable change in the vortex pattern as the applied field varies, but the moment is nearly constant. Magnetization reversal is sudden. When a field is applied oblique to the easy axis the magnetization is rather uniform in most of the particle. When an in-plane field is applied exactly along the hard axis, a complex domain structure is formed, so that the remanence is zero, in agreement with experiment. Formation of this state requires that the applied field exceed a critical value. Upon application of an easy axis field to this complex state, the domain structure is shifted so that the magnetization increases linearly with the applied field.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the effects of particle size and aspect ratio on the hysteresis in controlled arrays of small magnetic particles. The arrays of permalloy particles were fabricated via electron-beam lithography. Each array consists of ∼ 106 identical, uniformly spaced particles. Hysteresis loops measured with an alternating-gradient magnetometer for particles ∼5–0.1 μm are presented. We find an increase in the coercive force as the particle width decreases below 0.3 μm due to a change in the switching mechanism from domain-wall nucleation and wall motion to vortex nucleation and vortex motion. A novel angular dependence of the loops is described in detail. Results from ab initio micromagnetic calculations on isolated rectangular Permalloy particles are compared, where applicable, with the measurements. We find excellent qualitative and, in selected cases, quantitative agreement between the experiments and calculations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5544-5548 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of first-principles calculations of the magnetic behavior of particles of varying shapes (sphere, prolate spheroid, and rectangular particles of various aspect ratios) and sizes ranging from ≈0.1 to 10 μm. We use a numerical implementation of micromagnetics in which the only input quantities, aside from the particle geometry, are the material parameters and the magnetic history. We have obtained quantitative agreement with theory for spherical particles and qualitative agreement with experiment in the case of rectangular objects, and we have observed a variety of interesting reversible and irreversible phenomena accompanying magnetic reversal in all objects. We describe key aspects of the numerical implementation and survey selected results.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5877-5879 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of some numerical simulations are presented that model the behavior of the magnetic force microscope under various probe/sample configurations. Analysis is carried out under the assumption of uniform magnetization of an axially symmetric probe of various types including: sphere, cylinder, conical tip, and rounded magnetically coated conical tip. In these cases the analysis can be made by studying the effective magnetic surface charge on the probe. We also consider the case of a spherical probe with magnetization that can rotate in response to the local field. The sample configurations studied are also of the axially symmetric type, which can be used to model the fields generated by arrays of cylindrical samples, e.g., alumite.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4508-4508 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bifurcation analysis has been applied to nucleation of magnetization reversal by curling1 in spherical particles. Nucleation is a pitchfork bifurcation, with the external magnetic field as control parameter. Curling occurs as a local minimum of the energy when it exists as a solution of Brown's nonlinear equation2 for external field in excess of the critical value for curling. The existence of such a solution can be determined from second-order perturbation theory. When it exists, the magnetization varies continuously as the external field exceeds the critical value; otherwise, it must suffer a discontinuity. We have computed the solutions to Brown's equation to second order near nucleation. The transition is always a continuous one when the anisotropy constant K is not sufficiently large.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an experimental study of the thermally activated switching of the magnetization of individual isolated γ-Fe2O3 particles. These particles are prolate ellipsoids ∼3000 A(ring) long and 650 A(ring) wide. The measured angular dependence of the switching field, Hs(θ), is consistent at large angles with a uniform rotation, but as θ approaches zero, other modes of reversal appear possible, and most likely the mode of reversal is curling. By measuring the probability of reversal of the moment as a function of time and applied magnetic field at T∼300 K, we found that the switching was thermally assisted, but couldn't be described by hopping over a single energy barrier. Our results indicate that the dynamics of switching are described by a complex path in the energy landscape.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3179-3181 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a numerical approach to micromagnetic problems based on the finite element method. We discuss a convergence difficulty in three dimensions and we propose a solution which retains the local character of the numerical method. The shape anisotropy of each element is treated on the same footing as the crystalline anisotropy. Some tests of the validity of our original method in two dimensions are also described.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3435-3437 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nucleation of the uniform rotation mode for uniaxial ferromagnets is rigorously determined including the second anisotropy constant K2. The results show that the value of K2 will affect both the hysteresis loop and nucleation field significantly. For example, the square loops, for the easy axis direction, are rounded for certain values of K2. The relation Hk=2K1/MS needs to be modified when K2 is taken into account. Modified astroids are used to analyze the angular dependence of hysteresis loop. The calculated angular variation of Hc show bell-, M-, and W-type dependence. For certain values of second anisotropy the easy axis may be oblique to the c axis.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...