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  • 1
    Electronic Resource
    Electronic Resource
    The influence of interfacial exchange on the coercivity of acicular coated particle (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7756-7761 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The acicular coated magnetic particles are considered as magnetostatic interacting dual-component particles with interfacial exchange coupling. The calculations show that the coercivity varies with shell thickness and the relative magnetic properties between core and shell. When increasing the shell thickness, it is found that the initial slope of the increasing coercivity depends on the anisotropy energy of the shell, while the saturation level of the coercivity depends on the interfacial interaction. The calculated results show that a thin layer of shell is responsible for the increase of the coercivity. The best fitting curve for the available experimental data gives interfacial exchange coupling, A=5.87×10−8 erg/cm, and shell anisotropy constant, K=0.52×106 erg/cm3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347501
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  • 2
    Electronic Resource
    Electronic Resource
    Nonlinear effect of small volume fraction on the coercivity for acicular particles : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6659-6661 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Origins of nonlinear dependence of the coercivity on the volume fraction for an assembly of acicular particles are investigated. For a very small volume fraction, the nonlinear relationship between the coercivity and the volume fraction is attributed to the nonuniform distribution of particles and the surface effects. Considering the influence of surface, we find the coercivity can be either increasing or decreasing for a small volume fraction with different surface anisotropy constant Ks. Observed results agree with predictions based on the present model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352547
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  • 3
    Electronic Resource
    Electronic Resource
    The coercivity of particle arrays : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6662-6664 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal effects in an array of nonidentical, noninteracting single domain ferromagnetic particles are studied. Two sources of stochasticity are recognized within the array: the intrinsic stochastic nature of thermal relaxation and variations within the particles' volume and orientation with respect to applied field, both are discussed in turn. We use the log-normal volume distribution {∼(σV)−1exp[−ln2(V/V0)/(2σ2)]} and a cosν ψ angular distribution to calculate the mean coercivity B¯c of a particle array. We find that B¯c increases rapidly with increasing average volume 〈V(approximately-greater-than)=V0 exp(σ2/2) while for misaligned particles (ν≤∞) we observe a sudden decrease in B¯c accompanied by a gradual loss of frequency dependence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352548
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  • 4
    Electronic Resource
    Electronic Resource
    Coercivity of porous acicular particles (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7504-7509 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It has been suggested that the porosity in the magnetic particle has the crucial effect upon observed low coercivity, as compared with predictions of single-domain theory. However, the influence of the inner pores was never theoretically analyzed. When interactions among the pores are considered, we found that the coercivity of a single-domain particle depends on not only the porosity but also the number of pores. Moreover, in some cases the porosity increases the coercive force, in others it decreases it. When the pore number is large, the relationship between coercive force and porosity is quite linear. The magnetization of the particle is always decreasing as porosity increases. It was also found that the oblique angle between the inner pore and magnetic particle results in the decrease of the coercivity. To increase the coercivity, it is concluded that the pore shape is more important than the reduction of the porosity and the alignment of the pore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349724
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  • 5
    Electronic Resource
    Electronic Resource
    Micromagnetic studies of coherent rotation with quartic crystalline anisotropy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2431-2439 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nucleation fields under coherent rotation for uniaxial ferromagnets are rigorously determined including the second anisotropy constant K2. Theoretical studies cover the whole range of the relationships between K1 and K2. We show that the reversal processes can be classified into eight types depending on the parameters characterizing the magnetic materials. The results show that the value of K2 affects both the hysteresis loop and nucleation field significantly. The nucleation field along the c-axis is not always equal to 2K1/Ms. For certain values of second anisotropy, the easy axes may be oblique to the c-axis. When the ratio of K2 and K1 is large, the easy cone or hard cone will form at a certain oblique angle. The effects of K2 on the saturation field of hard axis loops have also been investigated. It is suggested that the values of K1 and K2 can be determined independently from the slope and saturation field of hard axis loops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348678
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  • 6
    Electronic Resource
    Electronic Resource
    Demagnetizing influence on the hysteresis loop of a perpendicular medium with columnar structure (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5184-5186 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a simple three-dimensional particulate model with average interaction field to calculate hysteresis behavior of a perpendicular medium with columnar structure. The influence of the thickness of thin film, gap between the columns, and direction of growth, Δω50, on the hysteresis loops are investigated. From the simulation results, we can conclude that the coercivity critically depends on the thickness. The coercivity of the in-plane loop is quite sensitive to the direction of growth, while the perpendicular loop is not. If the columns are not perfectly aligned, the in-plane loop will open. The larger Δω50 results in the larger opening. The only significant contribution from the variation of the gap between the columns is to change the anomalous shearing of the hysteresis loop. Our model was used to calculate minor loops. For the perpendicular direction, the minor loops are always quite flat and merge to the major loop, while for the in-plane loops they are asymmetrical to the origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344656
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of roughness on magnetic surface anisotropy in ultrathin films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 596-600 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetostatic model for shape anisotropy of an ultrathin film with surface roughness is presented. Apart from the usual volume anisotropy, an additional perpendicular surface anisotropy results from the surface roughness. For a continuous film, the shape anisotropy follows the famous 1/t behavior. By considering the correlation between the surfaces, the perpendicular surface anisotropy can be further increased. When the film thickness is less than a certain value, the magnetic layer may become a discontinuous or island-like structure and the shape anisotropy is proportionally lower with decreasing film thickness. With a nonzero quality factor (Q=Kc/2πMs2), a marked kink in the dependence Kefft on the film thickness gradually appears with increasing roughness. Observed results agree qualitatively with predictions based on the present model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351838
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature-dependence of interlayer exchange bias coupling in NiO/Cu/NiFe (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7540-7542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The trilayers 10 nm NiO(AF)/X Cu/10 nm NiFe(FM) were prepared for the study on the temperature effect in interlayer exchange bias coupling. The characteristic behavior of the interlayer exchange bias coupling as a function the spacer thickness was shown to strongly depend on the temperature. A monotonic decrease of the exchange bias field with increasing Cu spacer layer was observed at low temperature around 20 K. At higher temperatures (about 145 K), a clear oscillatory evolution of the exchange bias field with the Cu thickness was found even without background subtraction. The temperature-dependent feature of the interlayer exchange bias coupling was also found to vary significantly with different Cu thickness. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1361259
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  • 9
    Electronic Resource
    Electronic Resource
    Master equation approach to anhysteresis of noninteracting particles : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5487-5489 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hysteresis in an array of thermally relaxing, aligned, noninteracting uniaxial particles driven by a periodic applied field with an attenuating amplitude and a dc bias is studied. The asymptotic state reached after the ac component attenuated to zero has the characteristics of anhysteretic magnetization. The convergence of the solution is studied, the anhysteresis curve is shown to lie below the curve of the equilibrium magnetization, a heuristic formula for the initial anhysteretic susceptibility is proposed, and the effects of interparticle interactions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355715
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal stability of coated two phase magnets : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5145-5147 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A possible way to make high energy product magnets with surface coated soft phase based grains was proposed. It was proven theoretically that the energy product can easily achieve 70 MGOe with reasonable packing density and particle diameter. Here we analyze the thermal stability for these two phase magnets using a master equation with two metastable states for an individual grain, and then including the interaction from an oriented array. The result shows that an energy product of 60 MGOe can be maintained up to 400 K for a Nd2Fe14B/α-Fe system at packing density 0.8. ©1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365151
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