Micromagnetic Microscopy and Modeling

Dahlberg, E. Dan; Zhu, Jian‐Gang

doi:10.1063/1.881447

Cited by 100 publications

(44 citation statements)

References 9 publications

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“…In Fig. 2b we plotted the frequency of front oscillations vs. the field gradient according to (12) and as obtained from (1). Again, the agreement is excellent, and remains good even for c of order unity.…”

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confidence: 66%

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Controlling Domain Patterns Far from Equilibrium

et al. 1996

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A high degree of control over the structure and dynamics of domain patterns in nonequilibrium systems can be achieved by applying nonuniform external fields near parity breaking front bifurcations. An external field with a linear spatial profile stabilizes a propagating front at a fixed position or induces oscillations with frequency that scales like the square root of the field gradient. Nonmonotonic profiles produce a variety of patterns with controllable wavelengths, domain sizes, and frequencies and phases of oscillations.PACS numbers: 05.45.+r, 82.20Mj Technological applications of pattern forming systems are largely unexplored. The few applications that have been pursued, however, have had enormous technological impacts. Magnetic domain patterns in memory devices provide an excellent example [1]. Intensive research effort has been devoted recently to dissipative systems held far from thermal equilibrium [2]. Unlike magnetic materials, such systems are nongradient in general and their asymptotic behaviors need not be stationary; a variety of dynamical behaviors can be realized, including planar and circular traveling waves, rotating spiral waves, breathing structures and spatiotemporal chaos. This wealth of behaviors opens up new opportunities for potential technological applications. Their realizations, however, depend on the ability to control spatiotemporal patterns by weak external forces. Most studies in this direction have focused on drifting localized structures [3].In this paper we present a novel way to control domain patterns far from equilibrium. We consider dissipative systems exhibiting parity breaking front bifurcations (also referred to as nonequilibrium Ising-Bloch or NIB transitions [4,5]), in which stationary fronts lose stability to pairs of counterpropagating fronts. Examples of systems exhibiting NIB bifurcations include liquid crystals [6] and anisotropic ferromagnets [7] subjected to rotating magnetic fields, chains of coupled electrical oscillators [8], the catalytic CO oxidation on a platinum surface [9,10], the ferrocyanide-iodate-sulphite (FIS) reaction [11], and semiconductor etalons [12]. A prominent feature of these systems is that transitions between the parity broken states, the left and right propagating fronts, become feasible as the front bifurcation is approached. Indeed, intrinsic disturbances, like front curvature and front interactions, are sufficient to induce spontaneous transitions and can lead to complex pattern formation phenomena such as breathing labyrinths, spot replication [11,13] and spiral turbulence [14]. It is this dynamical flexibility near NIB bifurcations that we wish to exploit. By forcing transitions between the left and right propagating fronts, using spatially dependent external fields, we propose to obtain a high degree of control on pattern behavior.We demonstrate this idea using a forced activatorinhibitor system of the formwhere u, the activator, and v, the inhibitor, are scalar real fields, and h and J are external fields. With appropriate c...

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confidence: 66%

“…The few applications that have been pursued, however, have had enormous technological impacts. Magnetic domain patterns in memory devices provide an excellent example [1]. Intensive research effort has been devoted recently to dissipative systems held far from thermal equilibrium [2].…”

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confidence: 99%

Controlling Domain Patterns Far from Equilibrium

et al. 1996

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“…There are a variety of microscopic techniques with submicron resolution for detecting the magnetic structures of materials, 1 e.g., magnetic force microscopy ͑MFM͒, [2][3][4][5] Lorentz microscopy, 6,7 Foucault microscopy, 8 electron holography, 9,10 scanning electron microscopy with polarization analysis [11][12][13] and magneto-optic microscopy. 14 However, these techniques do not detect the dynamic features of the surface roughness caused by the external magnetic field.…”

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confidence: 99%

Magnetic domain and domain-wall imaging of submicron Co dots by probing the magnetostrictive response using atomic force microscopy

Wittborn

Rao

Nogués

et al. 2000

Applied Physics Letters

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An approach to image the domains and domain walls of small ferromagnetic entities using atomic force microscopy (AFM), with a nonmagnetic AFM probe, has been developed. Exciting the sample in an external ac magnetic field, the distribution of magnetostrictive response at the surface is detected. By this technique, the domains and domain walls of submicron Co dots have been imaged with a 1 nm lateral resolution. In elliptical Co dots with a 350-nm-long axis on a triangular lattice array with 400 nm periodicity, we find evidence for two domains with opposite magnetization orientation across a wall. The domain-wall width in these dots is found to be about 35 nm. Furthermore, we observe a ferromagnetic alignment of the domains in the neighboring dots, which suggests a magnetostatic interaction among the dots.

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“…The finite element method is a highly flexible tool to describe magnetization processes, since it is possible to incorporate the physical grain structure and intergranular phases and to adjust the finite element mesh according to the local magnetization [4,5]. The comparison of simulations and experiments can provide useful hints for artificial structuring of the material, in order to tailor the magnetic properties according to their specific applications [6].…”

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confidence: 99%