Magnetic block array for patterned magnetic media

Koike, Kazuyuki; Matsuyama, Hidetoshi; Hirayama, Yoshiyuki; Tanahashi, Kôtarô; Kanemura, T.; Kitakami, Osamu; Shimada, Yutaka

doi:10.1063/1.1345804

Cited by 40 publications

(19 citation statements)

References 21 publications

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“…For vertically magnetized particles the octopole moment reaches 25% of the dipole moment in the limit of small thicknesses. This geometry corresponds to sizes of particles often used in experimental studies [135,136,151,152]. For vertically elongated particles, such as arrays of magnetic nanocolumns [136,138] or liquid colloidal crystals with rod-like components [153] (see Fig.…”

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confidence: 99%

Influence of the lattice discreteness on magnetic ordering in nanostructures and nanoarrays

Vedmedenko¹

2007

Physica Status Solidi (b)

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.+ aThe article attempts to analyze the effect of lattice discreteness on the magnetic ordering in nanostructures and nanoarrays. The discussion starts with a basic introduction of the theoretical methods for the description of the magnetic ordering. Next it is shown that the discrete nature of an atomic lattice may lead to the size-driven reorientation of magnetization in nanoparticles, i.e., the magnetization direction can be changed by shrinking the lateral size, keeping the thickness fixed. It is demonstrated that in finite nanomagnets the shape anisotropy can be divided into the discrete and continuum contributions. Then the orientation of magnetic domain walls in low-symmetry objects is discussed. It is shown theoretically that in nanomagnets of monolayer thickness the mechanism of the orientation of domain walls is different from that of bulk systems and is mainly determined by the discreteness of the atomic lattice and the exchange energy. In the last part the theoretical study of magnetostatically interacting nanoarrays is presented. Special attention is paid to the influence of the underlaying lattice symmetry and the higher order multipolar terms on the magnetic ordering. It is demonstrated that the multipole-multipole interactions lead to an enhancement/decrease of the coercivity in arrays with in-plane/out-of-plane magnetization, respectively. In each section of the manuscript the agreement between the theory and recent experimental results is analyzed.

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confidence: 99%

Influence of the lattice discreteness on magnetic ordering in nanostructures and nanoarrays

Vedmedenko¹

2007

Physica Status Solidi (b)

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“…Good candidates for that are arrays of nanodots [22] and nanopillars [23]. For instance, dot arrays with a period of 70 nm have been fabricated [24], corresponding to H 1 ≈ 0.4 T, which is already a remarkably high field. Besides improving the critical fields, the dipole array field compensator can also be used to design logical devices in which superconductivity is controlled by switching between the two polarities of the magnetized dot array.…”

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Nanoengineered Magnetic-Field-Induced Superconductivity

et al. 2003

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The perpendicular critical fields of a superconducting film have been strongly enhanced by using a nanoengineered lattice of magnetic dots (dipoles) on top of the film. Magnetic-field-induced superconductivity is observed in these hybrid superconductor / ferromagnet systems due to the compensation of the applied field between the dots by the stray field of the dipole array. By switching between different magnetic states of the nanoengineered field compensator, the critical parameters of the superconductor can be effectively controlled. When the applied magnetic field exceeds a certain critical value, superconductivity is suppressed due to orbital and spin pair breaking effects. This very general property of superconductors sets strong limits for their practical applications, since, in addition to applied magnetic fields, the current sent through a superconductor also generates magnetic fields, which can lead to a loss of zero resistance. Materials that are not only able to withstand magnetic fields, but in which superconductivity can even be induced by applying a magnetic field, are very rare and up to now only (EuSn)Mo 6 S 8 [1, 2], organic λ-(BETS) 2 FeCl 4 materials [4,5] and HoMo 6 S 8 [3] show this unusual behavior. The appearance of magnetic-fieldinduced superconductivity (FIS) in the former two compounds was interpreted in terms of the Jaccarino-Peter effect [6], in which the exchange fields from the paramagnetic ions compensate an applied magnetic field, so that the destructive action of the field is neutralized. Here we report that FIS can also be realized in hybrid superconductor / ferromagnet nanostructured bilayers. The basic idea is quite straightforward (see Fig. 1): a lattice of magnetic dots with magnetic moments aligned along the positive z-direction is placed on top of a superconducting film. The magnetic stray field of each dot has a positive z-component of the magnetic induction B z under the dots and a negative one in the area between the dots. Added to a homogeneous magnetic field H, see Fig. 1(b), these dipole fields enhance the z-component of the effective magnetic field µ 0 H ef f = µ 0 H + B z in the small area just under the dots and, at the expense of that, reduce H ef f everywhere else in the Pb film, thus providing the condition necessary for the FIS observation. This new field compensation effect is not restricted to specific superconductors, so that FIS could be achieved in any superconducting film with a lattice of magnetic dots. To implement the idea of the nanoengineered FIS, we have prepared a sample, which reminds us of other systems used during the last decade for studying flux pinning by periodic arrays of magnetic dots

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“…Patterned magnetic media where magnetic bits are recorded on pre-defined, single-domain islands of an island array is one of the proposed approaches for extending magnetic storage densities beyond the limit set by thermal decay for conventional media [1][2][3]. Extensive studies on patterned magnetic media were performed primarily on the fabrication methods supporting bit densities of up to 200 Gbit/in 2 [4][5][6][7][8][9][10]. A challenge of writing to patterned media is that the write pulses must be synchronized to the media patterning in contrast to writing to conventional media where the bits can be placed everywhere on the medium.…”

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confidence: 99%

Magnetic reversal of sub-100 nm nanostructures studied by a FIB-trimmed recording head

et al. 2006

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Arrays of sub-100 nm square islands have been fabricated by patterning perpendicular Co 70 Cr 18 Pt 12 continuous films using focused ion beam (FIB) lithography. The recording studies were performed on a quasistatic write/read tester using FIB trimmed recording heads with a write width of about 100 nm. We demonstrate the ability to write controlled magnetic patterns by addressing individual single-domain islands in dense island arrays achieving bit densities as high as 60 Gbit/in 2 and to read back the written information. The range of write current over which single islands can be written is modeled using a write model which includes the write field distribution and the island switching field distribution. A window is found over which individual islands can be addressed without switching nearest neighbors.

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Magnetic block array for patterned magnetic media

Cited by 40 publications

References 21 publications

Influence of the lattice discreteness on magnetic ordering in nanostructures and nanoarrays

Influence of the lattice discreteness on magnetic ordering in nanostructures and nanoarrays

Nanoengineered Magnetic-Field-Induced Superconductivity

Magnetic reversal of sub-100 nm nanostructures studied by a FIB-trimmed recording head

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