Stray fields above artificial magnetic in-plane domains

Ahrend, Florian; Holzinger, Dennis; Fohler, Manuel; Pofahl, S.; Wolff, Ulrike; DeKieviet, Maarten; Schaefer, Rafael F.; Ehresmann, A.

doi:10.1016/j.jmmm.2015.01.003

Cited by 15 publications

(34 citation statements)

References 30 publications

(39 reference statements)

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“…During the experiments, particles were kept in a defined height range above the substrate surface where measurements of the EB substrate's MFL are available and the analytical model can be used to quantitatively describe the MFL. 15 For a proof-of-principle experiment, the 700 nm high resist structure was preserved ( Figure 1). As the particles pass the 5 μm wide gaps at an average time of 125 ms, the distance they are falling by the combined action of gravity and buoyancy while traversing the gaps of the resist structure was estimated to be Δz = 25 nm.…”

Section: Resultsmentioning

confidence: 99%

“…13 Recently, the magnetic field landscape as a function of position was experimentally determined by μ-Hall probe measurements within a height range between 0.75 and 2.65 μm over the sample surface. 15 It was shown there, that the MFL in this height range can be reasonably well described by an analytical model which will be also employed here. The model is based on the description of the change of magnetization when passing from one domain to the other over a domain wall by the empirical function 18…”

Section: Theoretical Modelmentioning

confidence: 93%

“…The quantitative determination of the MFL via μ-Hall measurements revealed the magnitude of the magnetic field as a function of the z-distance above the sample surface (H z (z)) at an x-position in the center of the domain wall. 15 The observed data was fitted by eq 4b, where a and M r were chosen as free fit parameters. The domain transition parameter was determined to a ≈ 150 nm, corresponding to a domain transition length of l W ≈ 450 nm, 15 the fit parameter for the remanent magnetization was M r = 41 kA/m according to the Co 70 Fe 30 layer thickness of 6.5 nm.…”

Section: Articlementioning

confidence: 99%

“…The particle transport process will be quantitatively modeled for a sequence of designed homogeneous external magnetic fields pulses for a particleÀsubstrate distance range where the substrate's MFL is quantitatively available. 15 The theoretically predicted particle velocity will be tested by corresponding quantitative experiments. The difference between the particle velocity and the velocity of the potential energy minimum in combination with the width of the artificial parallel stripe domains determine the threshold frequency of the external magnetic field pulses above which no directed particle motion occurs.…”

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confidence: 99%

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Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation

2015

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An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.

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Section: Resultsmentioning

confidence: 99%

Section: Theoretical Modelmentioning

confidence: 93%

Section: Articlementioning

confidence: 99%

mentioning

confidence: 99%

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Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation

2015

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“…For all three cases, the typical rainbow color pattern was still observed with almost no change of the optical color impression (Figure S3, Supporting Information). This result is expected as the spatially shaped MFL is much more pronounced in close proximity to the substrate, i.e., about a few microns in distance …”

Section: Resultsmentioning

confidence: 69%

Smart Surfaces: Magnetically Switchable Light Diffraction through Actuation of Superparamagnetic Plate‐Like Microrods by Dynamic Magnetic Stray Field Landscapes

Koch

Granath

Heß

et al. 2018

Advanced Optical Materials

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This work reports on a remotely controllable, all‐magnetic reflective diffraction grating‐like optical element for electromagnetic waves in the visible spectrum. The switchable grating is realized by the unique interplay between nanostructured superparamagnetic plate‐like microrods and a magnetic stray field landscape generated by an engineered magnetic stripe domain pattern superimposed by a small external magnetic field. It is shown that the purposeful design of local magnetic field sources in such a continuous thin‐film system enables a precise manipulation of the microrod alignment and, hence, dynamic control of the corresponding grating constant. It is demonstrated that the magnetic grating can be turned on and off due to disappearance of the engineered domain pattern when magnetically saturated. Moreover, the grating constant can be dynamically changed between two states when applying an AC external magnetic field. The experimental findings are corroborated by a theoretical model based on a quantitative description of the involved forces among the microrods and between microrods and substrate, respectively. These results therefore serve as a basis for smart surfaces with switchable diffraction properties on demand upon remote control.

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Selective Alignment of Molecular Glass Wrinkles by Engineered Magnetic Field Landscapes

Huckfeldt

Ahrend

Holzinger

et al. 2015

Adv Funct Materials

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A new approach for aligning wrinkles in thin viscoelastic polymethylmethacrylate films is established by sandwiching them between ferromagnetic layers. Experiments prove that a contribution from an engineered anisotropic 1D periodic magnetic stray field pattern can be decisive for the alignment of otherwise randomly oriented wrinkles at commensurate periods of the magnetic template pattern and the wrinkles. Alternatively, random wrinkling is observed under similar conditions, but when periodic magnetic stray fields are missing or not commensurate with the wrinkle wavelength. The possibility to stabilize two distinct types of wrinkling patterns in the same material system paves the way toward mechanically reconfigurable functional elements, enabling exciting possibilities for stretchable electronics, magnetic field sensors, and tuneable gratings for optoelectronics and photonics.

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Stray fields above artificial magnetic in-plane domains

Cited by 15 publications

References 30 publications

Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation

Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation

Smart Surfaces: Magnetically Switchable Light Diffraction through Actuation of Superparamagnetic Plate‐Like Microrods by Dynamic Magnetic Stray Field Landscapes

Selective Alignment of Molecular Glass Wrinkles by Engineered Magnetic Field Landscapes

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