A. V. Goncharov

Magnetic antidot arrays from self-assembly template methods

Using self assembly from lyotropic liquid crystalline phases and from colloidal suspensions of polystyrene spheres templates, we have prepared well-ordered, nanostructured magnetic materials. We present the results of electrochemical deposition of magnetic metals and alloys in the interstitial space between these templates. This technique has enabled us to create magnetic nanostructures with three-dimensional achitectures on length scales of 4 nm–1 μm. We find changes in coercive field, by more than 1 order of magnitude, dominated by the effects of the nanoscale shapes. Varying the parameters in the preparation allows us to produce materials with predetermined magnetic parameters. The templated electrodeposition technique offers the potential of a low-cost preparation method for submicron patterned magnetic media.

Oscillatory thickness dependence of the coercive field in magnetic three-dimensional antidot arrays

Recent developments in magnetic applications, such as data storage, sensors, and transducers, are stimulating intense research into magnetism on submicrometer-length scales. Emerging self-assembly fabrication techniques have been proposed as viable, low-cost methods to prepare such submicron structures. In this letter we present studies on magnetic nanostructures with 3D architectures, fabricated using a self-assembly template method. We find that the patterning transverse to the film plane, which is a unique feature of this method, governs the magnetic behavior. In particular, the coercive field, a key parameter for magnetic materials, was found to demonstrate an oscillatory dependence on film thickness.

In-plane anisotropy of coercive field in permalloy square ring arrays

Magnetic ring arrays are promising candidates for application in magnetic random access memory devices. The magnetic reversal processes and anisotropy of the coercivity in arrays of square-shaped nanorings with different spacings were investigated by vector magneto-optical Kerr effect magnetometry, magnetic force microscopy, and micromagnetic simulations. Two-step magnetization reversal demonstrates fourfold symmetry in the film plane resulting from the shape anisotropy in rings. Our numerical simulations show good agreement with the experiment.

Oscillatory thickness dependence of the coercive field in three-dimensional anti-dot arrays from self-assembly

We present studies on magnetic anti-dot nano-structures with three-dimensional (3D) architectures, fabricated using a self-assembly template method. We find that patterning transverse to the film plane, which is a unique feature of this method, results in novel magnetic behavior. In particular, one of the key parameters for a magnetic material, the coercive field Bc, was found to demonstrate an oscillatory dependence on film thickness.

Shape-induced anisotropy in antidot arrays from self-assembled templates

Using self-assembly of polystyrene spheres, well-ordered templates have been prepared on glass and silicon substrates. Strong guiding of self-assembly is obtained on photolithographically structured silicon substrates. Magnetic antidot arrays with three-dimensional architecture have been prepared by electrodeposition in the pores of these templates. The shape anisotropy demonstrates a crucial impact on magnetization reversal processes.

Shape induced anisotropy in hybrid anti-dot arrays from guided self-assembly templates

Ordered templates are used for electro-deposition of different magnetic materials. This technique offers new opportunities, which are not easily realized by standard lithographic methods, and which allows creation of magnetic nanostructures with 3D architectures on broad range of length scale. To address limitations of self-assembly, hybrid techniques using well established Si technology to guide and confine self-assembly templates is employed. Magnetic measurements are performed using superconducting quantum interference device (SQUID), a vibrating sample magnetometer and a magneto-optical Kerr effect rig. Electrical properties are studied using a four-point probe configuration. Magnetic structures have been imaged using magnetic force microscopy (MFM). Obtained results are analysed using micromagnetic simulations and simple analytical models of domain wall pinning and magnetization curling behavior.