Magnetism in reduced dimensions

Fruchart, Olivier; Thiaville, A.

doi:10.1016/j.crhy.2005.10.011

Cited by 52 publications

(41 citation statements)

References 150 publications

(161 reference statements)

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“…The dominant mode frequency is observed to be reduced by about 2 GHz as the element size is reduced from 124 to 70 nm, which might be indicative of a transition of the static magnetization state from an S state to a leaf state. 39 Consequently, the high amplitude regions have migrated to the edges of the element perpendicular to the bias field and slightly toward opposite diagonal corners where the effective field may be slightly reduced.…”

Section: B Size Dependencementioning

confidence: 99%

“…In the second method the bias field was applied 4°from the x direction, parallel to the uniaxial easy axis, so that all elements within the model array would have the same static magnetization state. It is known that OOMMF favors the flower 39 or X state due to the assumption of zero temperature. 20 However, the S state 39 can be stabilized at finite temperatures.…”

Section: B Numerical Simulationsmentioning

confidence: 99%

“…It is known that OOMMF favors the flower 39 or X state due to the assumption of zero temperature. 20 However, the S state 39 can be stabilized at finite temperatures. 20 We have also found that rounding of the element corners can promote the C state 39 in some elements ͓Fig.…”

Section: B Numerical Simulationsmentioning

confidence: 99%

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Time-resolved investigation of magnetization dynamics of arrays of nonellipsoidal nanomagnets with nonuniform ground states

et al. 2008

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Time-resolved scanning Kerr microscopy measurements have been performed upon arrays of square ferromagnetic nanoelements of different sizes and for a range of bias fields. The experimental results were compared to micromagnetic simulations of model arrays in order to understand the nonuniform precessional dynamics within the elements. In the experimental spectra acquired from an element of length of 236 nm and thickness of 13.6 nm, two branches of excited modes were observed to coexist above a particular bias field. Below this so-called crossover field, the higher frequency branch was observed to vanish. Micromagnetic simulations and Fourier imaging revealed that modes from the higher frequency branch had large amplitude at the center of the element where the effective field was parallel to the bias field and the static magnetization. Modes from the lower frequency branch had large amplitude near the edges of the element perpendicular to the bias field. The simulations revealed significant canting of the static magnetization and effective field away from the direction of the bias field in the edge regions. For the smallest element sizes and/or at low bias field values, the effective field was found to become antiparallel to the static magnetization. The simulations revealed that the majority of the modes were delocalized with finite amplitude throughout the element while the spatial character of a mode was found to be correlated with the spatial variation in the total effective field and the static magnetization state. The simulations also revealed that the frequencies of the edge modes are strongly affected by the spatial distribution of the static magnetization state both within an element and within its nearest neighbors. Furthermore, the simulations suggest that collective modes may be supported in arrays of interacting nanomagnets, which act as magnonic crystals.

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Section: B Size Dependencementioning

confidence: 99%

Section: B Numerical Simulationsmentioning

confidence: 99%

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Time-resolved investigation of magnetization dynamics of arrays of nonellipsoidal nanomagnets with nonuniform ground states

et al. 2008

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“…However, we can infer that in Mn 2 /GNRs, the MAE will be raised (in comparison with Mn dimers adsorbed on graphene sheets), because, due to the reduced symmetry along the edge sites, the spin-orbit coupling of the adsorbed dimers will be strengthened. 17 Because the electronic states near the Fermi level are mostly ruled by the edge states along the GNRs, the presence of the Mn dimers will play an important role in the spin-density configuration and the electronic band structure of Mn 2 / GNR. Indeed, as indicated in Fig.…”

mentioning

confidence: 99%

Mn dimers on graphene nanoribbons: An ab initio study

Rigo

Miwa

Silva

et al. 2011

Journal of Applied Physics

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We show, using ab initio density functional theory calculations, that Mn dimers adsorbed on graphene nanoribbons (Mn2/GNRs) present a magnetic bistability, as does the isolated Mn dimer. Our total energy results indicate that Mn dimers lying along the edge sites of zigzag GNRs represent the most likely configuration. We find that similar to the isolated Mn2 molecule, the antiferromagnetic coupling represents the ground state for Mn2/GNR, and the spin density configuration of the GNR does not play an important role on the net magnetic moment of Mn2, which makes GNRs an ideal substrate for adsorption of these molecules. The ground state and the excited state configuration of the Mn dimer, viz., low-spin (LS) and high-spin (HS), are maintained in the face of changes in the spin density configuration of the substrate. Here we find that the Mn2/GNR systems exhibit a LS ↔ HS binary behavior, which can be considered as a useful property in the development of nanomemories based upon metallic clusters.

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“…Sabe-se que para um objeto retangular sub-micrométrico a estrutura encontrada é de fechamento, enquanto que para um objeto circular ocorre a formação de vórtices. Alguns parâmetros como a anisotropia cristalina do filme magnético depositado, o tamanho dos objetos litografados, bem como o seu formato influenciam diretamente na formação do padrão da estrutura de domínios [Fru05,Hub98]. Em geral, o procedimento realizado é verificar qual a estrutura que se forma e como esta evolui com a aplicação de um campo magnético externo.…”

Section: Figura 12: Estudo De Vórtices Magnéticos Em Um Disco De Perunclassified

Estudo das propriedades magnéticas de um objeto microestruturado através do SNOM-MO

Pojar¹

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Dedico este trabalho aos meus pais e à minha família.iii AgradecimentosGostaria de agradecer as várias pessoas que contribuíram de forma direta ou indireta para a realização deste trabalho.Em especial, ao Toninho, pela oportunidade e voto de confiança para a realização deste trabalho, pela orientação e dedicação, sugestões e conselhos sempre dados de modo preciso e sempre pacientes, e principalmente pela sua amizade; Ao Seabra, pelos ensinamentos em sua área de pesquisa e principalmente pela paciência e insistência nas horas de dificuldade; Ao Jeroen, eterno amigo, que ensinou todos os detalhes e procedimentos no manuseio do SNOM de forma precisa e carinhosa; À Alessandro, Angela, Regina, Luiz, Narcizo, companheiros de trabalho que desde o início acompanharam os meus primeiros passos; À Gabriel, Simone, Gilderlon e Erick, valeu pela companhia, amizade e brincadeiras que tornaram o convívio no Laboratório mais carinhoso e agradável; Ao Sergio, Marcelo, Iran, Paulo e Marcos, obrigada pela predisposição e paciência por me ajudarem sempre; Aos meus Pais, minha avó, e meus irmãos (Renata, Camila e Divino), pelo apoio incondicional durante todos esses anos, desde os meus primeiros passos e em todos os momentos bons e ruins; pela infinita paciência e compreensão nas várias vezes que estive ausente, por ser o que vocês são... Sem vocês seria impossível essa minha caminhada. Optical Microscope (SNOM-MO) falls in this context due to be a technique of microscopy with high spatial resolution and magnetic sensitivity, estimated to be ∆M = 2 x 10 -12 emu. In contrast to traditional optical microscopes, SNOM deals with evanescent electromagnetic radiation and, consequently, the resolution is no longer limited by the Rayleigh criterion.The SNOM-MO is a powerful tool to obtain local magnetic information through differential susceptibility and local hysteresis loops. Using this last technique, an experimental micromagnetic mapping was made for the magnetization vector on a square amorphous CoFeSiBNb object. The experimental results obtained provided information about the two chiralities existing in its closure magnetic domain structure, whose behavior is determined mainly by the shape anisotropy. The study also showed that pinnings generated by defects on surface´s object exerted great influence on the dynamic of the magnetization vectors. Due to the large amount of local magnetic information, this kind of study becomes a potential background for the development of more accurate and complete theoretical models.The experimental results demonstrate resolution better than 125 nm. This study has allowed us to access intrinsic magnetic behaviors that motivated an interesting discussion about magnetic pinnings, rotation of magnetization, reversal magnetic fields and local anisotropy.In addition, also special attention was given to the optimization of instrumental technique in order to make the SNOM-MO a measurement instrument with nanometer resolution. Among these efforts we emphasize the production of tips by FIB technique and the int...

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Magnetism in reduced dimensions

Cited by 52 publications

References 150 publications

Time-resolved investigation of magnetization dynamics of arrays of nonellipsoidal nanomagnets with nonuniform ground states

Time-resolved investigation of magnetization dynamics of arrays of nonellipsoidal nanomagnets with nonuniform ground states

Mn dimers on graphene nanoribbons: An ab initio study

Estudo das propriedades magnéticas de um objeto microestruturado através do SNOM-MO

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