Simulations of the magnetization reversal of clustered Co-Cr particles

Kooten, M. van; Haan, S. de; Lodder, J.C.; Lyberatos, A.; Chantrell, R.W.; Miles, J.J.

doi:10.1016/0304-8853(93)91307-s

Cited by 16 publications

(9 citation statements)

References 10 publications

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“…This assumption is taken from Ref. 12 where micromagnetic calculations were performed for strongly interacting single-domain particles with perpendicular anisotropy. There, collective reversals were suggested based on a facilitating effect on the switching of neighboring particles during the reversal of a particle.…”

Section: Resultsmentioning

confidence: 99%

Magnetization of small arrays of interacting single-domain particles

Grundler

Meier

Broocks

et al. 1999

Journal of Applied Physics

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We have prepared tailored small arrays of single-domain Ni nanomagnets exhibiting an easy-axis perpendicular to the substrate surface. Using ballistic Hall micromagnetometry we probe the magnetization under different tilt angles. For an array of 13 nanomagnets with 700 nm spacing, we observe distinct plateau values in the hysteresis loop indicating the stepwise switching of these particles. The observed hierarchy of reversal comes close to a model on the basis of the magnetostatic interparticle interaction.

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Section: Resultsmentioning

confidence: 99%

Magnetization of small arrays of interacting single-domain particles

Grundler

Meier

Broocks

et al. 1999

Journal of Applied Physics

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“…In contradiction to this in an ideal hexagonal alumite structure one should expect the needles to reverse randomly, because the flux closure of a switched needle strengthens the position of the surrounding unswitched needles. In opposition to that the micromagnetic simulations of van Kooten [22] on arrays of perpendicular columnar Co-Cr structures suggest collective reversals. The neighbour needles interact by the in plane field component of the top layer of the needles, where the magnetization is inclined during the reversal.…”

Section: Lndilidual Needle Behauiourmentioning

confidence: 43%

Bitter colloid observations of magnetic structures in perpendicular magnetic recording media

Porthun

Berge

Lodder

1993

Journal of Magnetism and Magnetic Materials

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“…The interaction between "particles" is strictly magnetostatic. Due to regularity of the system, numerical calculation of the interaction field is straightforward [6]. The Preisach function and its integral (the total magnetization) can be obtained directly by counting the number of particles in up and down magnetized states.…”

Section: Resultsmentioning

confidence: 99%

Measurement of the switching properties of a regular 2-D array of Preisach-type particles

Pardavi‐Horváth

Vértesy

1994

IEEE Trans. Magn.

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One of the most important remaining issues in the theory of hysteresis is a complete description of the physical meaning of the parameters that define the model equations.' In common with the Stoner-Wohlfarth theory of rotational processes, the theory of hysteresis provides one of the few theories of hysteresis based on underlying physical mechanisms, rather than curve fitting models. In this paper, it is shown that the parameter a, which governs the orientation of the anhysteretic curve, is related to the density of domains and the absolute temperature a=kBT/ pe(m), where (m) is the magnet moment of the average domain in the material, measured in Am'. In fact, the magnetic material can be treated thermodynamically as an assembly of pseudodomains, each with identical magnetic moment (m), and each interacting with all the other domains via the coupling coefficient a, leading to a mean coupling field of aM. The pinning coefficient k is simply a measure of the energy dissipation caused by movement of domain walls. The dissipation energy is proportional to the change in magnetization, dE=yokdM.Finally, the reversible component of magnetization is due principally to domain wall bending, and the bending coefficient c is related to the domain wall surface energy y, the average domain magnetization (m), and the spacing between pinning sites 1, according to the equation c= ( (m)pI4/4~> * F,,, where Fm, is the maximum force exerted on the domain wall by a typical pinning site. This means that the amount of domain wall bending increases with the strength of pinning sites (F,,,) and decreases in inverse proportion to the domain wall surface energy. In conclusion therefore it is possible to give an exact physical meaning for all of the parameters used in the theory of hysteresis. The original Preisach model of magnetic hysteresis assumes an assembly of single domain particles, each having a rectangular hysteresis loop. The loops are characterized by up and down switching fields. The halfwidth of the loop is the coercivity H, of the given particle. The loops might be shifted depending on the magnetic state of the environment, described by an effective interaction field, HP In the present work the switching properties of an artificially structured, highly uniaxial, magneto-optic garnet film (courtesy of R. Belt, AIRTRON), corresponding to the assumptions of the original Preisach model, are investigated. In t.his case the parameter identification is straightforward. The garnet film is etched into 42 pm rectangular pixels, separated by 15 pm grooves. Each pixel has a rectangular hysteresis loop. Up and down magnetized pixels give a black and white contrast due to Faraday effect. Magnetization can be measured by counting the number of pixels switched in a given field. The distribution of the coercive field has been obtained by measuring individual loops on each of several hundred pixels in an optical magnetometer. The average He=265 f 99 Oe, Hi= 0 f 26 Oe. The interaction field has been measured on the same pixel, depending on th...

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Simulations of the magnetization reversal of clustered Co-Cr particles

Cited by 16 publications

References 10 publications

Magnetization of small arrays of interacting single-domain particles

Magnetization of small arrays of interacting single-domain particles

Bitter colloid observations of magnetic structures in perpendicular magnetic recording media

Measurement of the switching properties of a regular 2-D array of Preisach-type particles

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