The effects of different demagnetisation processes on interaction effects in thin film media

El‐Hilo, M.; O’Grady, K.; Mayo, P.I.; Chantrell, R.W.; Sanders, I.L.; Howard, J. K.

doi:10.1109/20.179784

Cited by 36 publications

(23 citation statements)

References 9 publications

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“…18,19 The advantage of the FORC method over other approaches is the extreme sensitivity to microscopic details of hysteretic systems. Although the wealth of information a FORC diagram delivers still remains to be fully characterized, the method can be used as an extremely sensitive "fingerprint" of a hysteretic system.…”

Section: Outline Of the Forc Methodsmentioning

confidence: 99%

Finite versus zero-temperature hysteretic behavior of spin glasses: Experiment and theory

et al. 2007

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We present experimental results attempting to fingerprint nonanalyticities in the magnetization curves of spin glasses found by Katzgraber et al. [Phys. Rev. Lett. 89, 257202 (2002)] via zerotemperature Monte Carlo simulations of the Edwards-Anderson Ising spin glass. Our results show that the singularities at zero temperature due to the reversal-field memory effect are washed out by the finite temperatures of the experiments. The data are analyzed via the first order reversal curve (FORC) magnetic fingerprinting method. The experimental results are supported by Monte Carlo simulations of the Edwards-Anderson Ising spin glass at finite temperatures which agree qualitatively very well with the experimental results. This suggests that the hysteretic behavior of real Ising spinglass materials is well described by the Edwards-Anderson Ising spin glass. Furthermore, reversalfield memory is a purely zero-temperature effect.

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Section: Outline Of the Forc Methodsmentioning

confidence: 99%

Finite versus zero-temperature hysteretic behavior of spin glasses: Experiment and theory

et al. 2007

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“…A different approach, based on simulated annealing, has been used by Dean et al [83] to produce the ac erased state. A recent study [84] has shown that the IRM curve is very strongly dependent on the details of the erasure process. the lowest energy state of the system.…”

Section: Remanence Curve Studiesmentioning

confidence: 99%

The Magnetic Properties of Fine Particles

Chantrell

O’Grady

1994

Applied Magnetism

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Magnetic fine particles find a large number of applications, perhaps most notably as particulate recording media. In addition, the ideas of fine particle magnetism are applicable in a number of areas as diverse as geomagnetism and biomagnetism. The purpose of this chapter is to introduce the fundamental aspects of fine particle magnets, including magnetisation reversal phenomena, interaction effects and time dependence, and to describe applications to geomagnetism and recording media. UNITS Note that in this chapter cgs units are used throughout, with the relationship between flux density, field strength and magnetization being B = H + M with M = 47r1. 113 115shown. It can be seen that the alignment increases both the value of He and the remanent magnetisation Mr' For this reason particulate recording media are magnetically aligned to some degree as will be seen later. INTRINSIC PARTICLE PROPERTIESThe magnetic behaviour of a fine particle system is to a large extent governed by the intrinsic properties of the particles. The most important property is the magnetic anisotropy, which, as will be seen later, provides an energy barrier to magnetisation rotation which, importantly, can be large enough to result in irreversible magnetic behaviour. The anisotropy arises from three main effects: * * * Crystalline Anisotropy. This has its ongm in the non-spherical shape of electron orbitals which give rise to preferred orientations in the lattice. The second necessary factor is a strong spin-orbit coupling which links the magnetic moment to the spatial anisotropy. The result is an energy term having the symmetry of the crystal lattice. The two most familiar forms are uniaxial anisotropy Ea = K 1 sin 2 8 + K 2 sin 4 8 and cubic anisotropy:where (a,,8,1) are the direction cosines. For the case of uniaxial anisotropy it is often found that Kl»K2 and only the first term is retained.Shape Anisotropy. In any magnetised body there exist demagnetising fields due to free poles on the surface. For a non-spherical body the demagnetising effects are anisotropic. This leads (for an ellipsoid of revolution) to an anisotropy energy which is uniaxial in form with an anisotropy constant K = 1/2(NB -NA)I;b where NB and N A are the demagnetising factors along the principal axes of the ellipsoid.Strain Anisotropy. This is essentially a magnetostrictive effect and is often described by a uniaxial anisotropy with an effective anisotropy constant K" = ~).s 0' where >-s is the saturation magnetostriction.The particle anisotropy represents one of the dominant factors in the behaviour of a fine particle, the second major factor being its size which, as will be seen later, is largely responsible for determining the mode of magnetisation reversal. It should also be noted that the particle surface plays an important role in relation to the magnetic behaviour. For example, the loss of exchange coupling in the surface can lead to a reduction in the magnetisation of the particle. In addition, there exists the possibility of various types of spin-pinning...

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“…2. Compositions of films were examined with an EDX spectrometer, and the magnetic properties including the magnetization M , coercivity H c , intergrain interaction behavior ⌬M , 3 and the magnetic switching volume or magnetic grain, 4,5 were measured with an alternating gradient force magnetometer.…”

Section: Methodsmentioning

confidence: 99%