Micromagnetics of ferromagnetic equilateral triangular prisms

Koltsov, Denis; Cowburn, R. P.; Welland, Mark E.

doi:10.1063/1.1315618

Cited by 38 publications

(33 citation statements)

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“…3(d). When the triangles are saturated from base to tip (h ¼ 90 ), the resulting remanent configuration is similar to a "buckle" state 31,32 (the magnetization bends parallel to the base and then rotates to the tip), as shown in Fig. 3(e).…”

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confidence: 87%

“…It is close to zero in the loops of array A and in the h ¼ 0 loop of array B; in contrast, the vortex nucleation in the h ¼ 90 loop of array B occurs at a positive field H n % 120 Oe. As shown in previous studies, 31,32 carried out in low anisotropy materials, the directions parallel to the triangle sides correspond to easy axes from the point of view of the MSE. On the contrary, the MSE is maximal when the triangle is magnetized along the base-to-tip or shape-equivalent directions due to the large density of poles at the triangle base and to the large dipolar (demagnetizing) field they create.…”

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confidence: 99%

“…This induces the well-known six-fold configurational anisotropy of nanotriangles, with an energy maximum every 60 . 32 In the case of array B, the magnetocrystalline anisotropy energy (MAE) is also maximum for h ¼ 90 , i.e., this direction corresponds to a hard MSE and MAE axis simultaneously, and, consequently, vortices nucleate even though the applied field is positive. The equivalent direction for array A is, on the other hand, an easy axis from the point of view of the MAE.…”

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confidence: 99%

“…No symmetric "y" state is stable according to simulations, in agreement with previous results on permalloy which indicate that this state can only be stabilized under very restrictive conditions (triangle size below 200 nm and sharp corners). 31,32 The vortices nucleate at one of the sides of the triangles and they move to the center, Fig. 3(f), and exit at the opposite corner, Fig.…”

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confidence: 99%

“…This increase is maximum (minimum) along the base-to-tip (base) and equivalent directions. 32 The uniform magnetization leads to a decrease in the exchange energy. Finally, we have to consider that keeping the magnetization parallel to a hard MAE axis requires a higher field than along an easy axis.…”

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Breaking the configurational anisotropy in Fe single crystal nanomagnets

Gómez

Cebollada

Palomares

et al. 2014

Applied Physics Letters

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In this work, we improve the ability to tailor the switching mechanism in nanomagnets by introducing an additional, highly controlled source of anisotropy: magnetocrystalline anisotropy. We analyze the vortex dynamics in single crystal Fe nanotriangles with different orientations of the crystalline axes. By experimental studies and simulation, we show that the angular dependence of the vortex annihilation field springs from the convolution of the crystalline and configurational anisotropies. In contrast, the remanence and the nucleation field present a much simpler behavior controlled by the existence of a single symmetry axis when shape and crystalline orientation are taken into account. Magnetic nanostructures have become a highly active research area due to their unique physical behavior and to their relevance in established and emerging technological fields such as spintronics, magnonics, magnetic storage, nanobiomagnetism, and high frequency and superconducting devices.1-7 A key issue in tailoring the hysteresis processes of magnetic nanostructures lies in the control of the different anisotropy energy contributions and their corresponding effective fields. 8,9 One of the main energy contributions in magnetic nanodots is due to the internal dipolar (demagnetizing) fields. These give rise to the so-called configurational anisotropy, [10][11][12] which is related to the geometry of the dots. The reduction of the large dipolar fields for dots in the range between the single and multidomain regime is accomplished through the formation closed-flux structures called vortices. [13][14][15][16][17] The hysteresis of vortex dynamics is characterized by two large magnetization jumps associated with the nucleation and annihilation of the vortices, respectively, and very low remanence due to their closed flux structure.10 Vortices nucleate at the dot edges upon decreasing the applied field from saturation at a field value called nucleation field H n . They traverse the dot when the applied field is reversed and they are finally expelled when the annihilation field H ann is reached.18-20 Vortex dynamics can be controlled using different strategies. As an example, the nucleation and annihilation sites can be selected and their corresponding nucleation and annihilation fields can be tuned by choosing the geometry of the dots in combination with the orientation of the applied field.19-25 Most studies have emphasized the relevance of the dipolar fields in controlling the hysteresis of dots. So far we know, the role of the magnetocrystalline anisotropy energy (MAE) has not been usually considered since most of the experimental studies in the literature deal with dots patterned on Permalloy 14,15,18,23 (low MAE) or on isotropic polycrystalline films 16,22,25 (no preferential crystalline orientation). However, MAE might become a major factor in the magnetization mechanisms of single crystal dots and, in fact, theoretical calculations indicate that it strongly affects the hysteresis parameters. 26In this paper, we present an ex...

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