Magnetocrystalline and configurational anisotropies in Fe nanostructures

Vavassori, P.; Bisero, D.; Carace, F.; Liberati, M.; Bona, A. di; Gazzadi, Gian Carlo; Valeri, Sergio

doi:10.1016/j.jmmm.2004.11.177

Cited by 5 publications

(4 citation statements)

References 6 publications

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“…To study the interplay between all these contributions in Fe micro and sub-micro magnets, we fabricated by focused ion beam (FIB) milling a set of arrays of single-crystal Fe elements on MgO [84,85]. FIB is a versatile nanofabrication tool based on the interaction of nanosize beams of energetic Ga ions with solid surfaces [86][87][88].…”

Section: Magnetic Properties At the Nanoscalementioning

confidence: 99%

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Metals on oxides: structure, morphology and interface chemistry

Valeri

Benedetti

Luches³

2007

J. Phys.: Condens. Matter

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In this paper we review our recent studies on the structure, morphology and interface chemistry of different metal systems on simple rock-salt oxides, providing a basis for the understanding of their properties.Fe on both MgO and NiO grows in the cubic structure with the (001)Fe (001)oxide and [110]Fe [100]oxide orientation.The Fe/MgO interface is sharp at the atomic level up to 400 • C, thus showing that MgO can allow the growth of 'free standing' Fe films and lowdimensional structures. Submicrometric Fe dots on MgO have been prepared by FIB milling and characterized by the magneto-optical Kerr effect. At the Fe/NiO(001) interface an Fe-Ni body centred tetragonal alloyed phase is formed on top of a two-dimensional FeO layer situated at the interface. The FeO layer presents an expansion of the interplanar distance at the interface and a buckling in the Fe and O atomic positions. The presence of the structurally distorted FeO phase is predicted by ab initio density functional theory calculations to increase the spin magnetic moment of Fe atoms by 0.6 μ B compared to the ideally abrupt interface. A reduction of NiO is also induced by the deposition of (supposedly) inert Au films, which incorporate the metallic Ni atoms. The reduction takes place at the low-coordination sites at the surface of the NiO film. The Co/MgO(001) system has also been studied. In all the investigated cases, given the lower surface free energy of the oxide surfaces compared to the metal ones, the deposited metals tend to form islands, which coalesce above a few monolayers.

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Section: Magnetic Properties At the Nanoscalementioning

confidence: 99%

“…with higher flexibility, enabling one-step maskless etching. Etching occurs by physical ion sputtering [84,89,90], optionally gas assisted to enhanced material removal rates or species selectivity [91].…”

Section: Magnetic Properties At the Nanoscalementioning

confidence: 99%

Metals on oxides: structure, morphology and interface chemistry

Valeri

Benedetti

Luches³

2007

J. Phys.: Condens. Matter

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“…Several previous studies have examined the effects of configurational anisotropy, but these have dealt mostly with two‐dimensional structures, and usually formed from patterned thin films of isotropic magnetic materials [ Koltsov et al , 2000; Torres et al , 2001; Vavassori et al , 2005]. For naturally occurring magnetic materials, the influence of configurational anisotropy has received little attention.…”

Section: Introductionmentioning

confidence: 99%

Configurational anisotropy in single‐domain and pseudosingle‐domain grains of magnetite

2006

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[1] In classical domain theory, single-domain (SD) grains change their magnetization by coherent rotation, where the energy barrier to domain reversal is provided by the magnetocrystalline anisotropy or by shape anisotropy for elongated grains. However, numerical micromagnetic models have shown that domain structure in SD grains is rarely perfectly uniform. For example, magnetite has significant ''flowering'' of its magnetization even in grains that approach the room temperature superparamagnetic (SP) size of $30 nm. The flowering deforms slightly to accommodate the grain shape and thereby produces anisotropy independent of magnetocrystalline effects but dependent on magnetization direction within the grain. This can be similar in magnitude to that of magnetocrystalline anisotropy, even for equidimensional grains (where distance from the centroid to the grain faces is equal). The interaction of the domain structure and grain geometry is termed configurational anisotropy and has been studied mainly in relation to man-made isotropic magnetic media but received little attention in rock magnetism. In this paper we examine configurational anisotropy in SD to pseudo-single-domain (PSD) grains of magnetite using a three-dimensional finite element/boundary integral (FEBI) micromagnetic model. Equidimensional grains of magnetite of three different shapes are considered: a cube, an octahedron, and a regular tetrahedron, and in each case the effects magnetocrystalline anisotropy were removed in order to isolate the configurational anisotropy. The numerical models predict that very large coercivities are possible even for SD equidimensional grains. For tetrahedral grains coercivities of $120 mT were obtained, which otherwise would require a grain elongation of $1:1.75. Depending on the orientation of the principle crystalline axis to the grain shape, the configurational anisotropy may increase or decrease the overall energy barrier to domain reversal.

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“…To study the interplay between magnetocrystalline and configurational anisotropies, we fabricated by FIB milling a set of arrays of Fe single crystal square elements on MgO [16,49]. In this system the intrinsic magnetocrystalline anisotropy of the Fe single crystal has a fourfold symmetry, which is the same main symmetry showed by the configurational anisotropy in square nanomagnets [45,47,48].…”

Section: Magnetic Anisotropies In Squared Fe Micromagnetsmentioning

confidence: 99%

Arrays of Metal Nanostructures Produced by Focussed Ion Beam

Luches¹,

Bona²,

Contri

et al. 2007

Acta Phys. Pol. A

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We present a study of the magnetic properties of arrays of nanostructures produced in a focussed ion beam-scanning electron microscope dual beam system. The single magnetic units have been isolated either by direct removal of parts of the metallic film or by local modification of the film magnetic properties. The final quality of the shape and the residual damage strictly depend on beam parameters (spot size and pixel dwell time) and on the swelling properties of the patterned materials. On square Fe(001) elements with a well-defined intrinsic (magnetocristalline) and shape-and size--induced (shape plus configurational) anisotropy we show that the overall magnetic anisotropy is not a mere superposition of the individual contributions. We also demonstrate that with ion irradiation doses below the milling threshold L10 FePt films with perpendicular magnetic anisotropy undergo a transition from the magnetically hard L1 0 phase to the magnetically soft A1 phase leading to an out-of-plane to in-plane spin reorientation. The magnetic properties of the planar arrays obtained by local modification of the film are compared to arrays of sculpted structures of the same material.

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Magnetocrystalline and configurational anisotropies in Fe nanostructures

Cited by 5 publications

References 6 publications

Metals on oxides: structure, morphology and interface chemistry

Metals on oxides: structure, morphology and interface chemistry

Configurational anisotropy in single‐domain and pseudosingle‐domain grains of magnetite

Arrays of Metal Nanostructures Produced by Focussed Ion Beam

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