Size effects of the magnetic anisotropy of fcc cobalt nanoparticles embedded in copper

Hillenkamp, Matthias; Oyarzún, Simón; Troc, Nicolas; Ramade, Julien; Tamion, Alexandre; Tournus, Florent; Dupuis, V.

doi:10.1140/epjd/e2017-80299-x

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…Quite similar to what has been observed in figure 6(b) at low temperatures (∼50 K), a change in the general trend of H K is documented for ferrites [72]. Figures 6(c) and (d) illustrates the decreasing general trend of the anisotropy field with size in both high and low temperatures which has been observed in different types of nanoparticle structures including iron oxide [75][76][77]. To better understand these changes, as well as many others, more in-depth studies are required.…”

Section: Resultssupporting

confidence: 81%

Emergent magnetism and exchange bias effect in iron oxide nanocubes with tunable phase and size

Attanayake¹,

Chanda²,

Das³

et al. 2022

J. Phys.: Condens. Matter

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We report a systematic investigation of the magnetic properties including the exchange bias (EB) effect in an iron oxide nanocube system with tunable phase and average size (10, 15, 24, 34, and 43 nm). X-ray diffraction and Raman spectroscopy reveal the presence of Fe3O4, FeO, and α-Fe2O3 phases in the nanocubes, in which the volume fraction of each phase varies depending upon particle size. While the Fe3O4 phase is dominant in all and tends to grow with increasing particle size, the FeO phase appears to coexist with the Fe3O4 phase in 10, 15, and 24 nm nanocubes but disappears in 34 and 43 nm nanocubes. The nanocubes exposed to air resulted in an α-Fe2O3 oxidized surface layer whose thickness scaled with particle size resulting in a shell made of α-Fe2O3 phase and a core containing Fe3O4 or a mixture of both Fe3O4 and FeO phases. Magnetometry indicates that the nanocubes undergo Morin (of the α-Fe2O3 phase) and Verwey (of the Fe3O4 phase) transitions at ~250 K and ~120 K, respectively. For smaller nanocubes (10, 15, and 24 nm), the exchange bias (EB) effect is observed below 200 K, of which the 15 nm nanocubes showed the most prominent EB with optimal antiferromagnetic (AFM) FeO phase. No EB is reported for larger nanocubes (34 and 43 nm). The observed EB effect is ascribed to the strong interfacial coupling between the ferrimagnetic (FiM) Fe3O4 phase and AFM FeO phase, while its absence is related to the disappearance of the FeO phase. The Fe3O4/ α-Fe2O3 (FiM/AFM) interfaces are found to have negligible influence on the EB. Our findings shed light on the complexity of the EB effect in mixed-phase iron oxide nanosystems and pave the way to design exchange-coupled nanomaterials with desirable magnetic properties for biomedical and spintronic applications.

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Section: Resultssupporting

confidence: 81%

Emergent magnetism and exchange bias effect in iron oxide nanocubes with tunable phase and size

Attanayake¹,

Chanda²,

Das³

et al. 2022

J. Phys.: Condens. Matter

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“…This is because the effective magnetic energy barrier of nanoparticles results from various contributions, namely, cubic magnetocrystalline, surface, shape and magnetoelastic anisotropy. Recent results indicate, that for Co nanoparticles with D < 3 nm the surface anisotropy is dominating, whereas for larger nanoparticles ( D > 3 nm) the shape anisotropy is decisive . It has been also found experimentally that for nearly spherical 20 nm fcc‐Co nanoparticles the presence of planar defects, such as twin boundaries and stacking faults, alter the magnetocrystalline anisotropy leading to dominating shape anisotropy that should be of the order of 10 5 erg/cm 3 (10 4 J m −3 ) .…”

Section: Resultsmentioning

confidence: 96%

Electronic Transport and Magnetic Properties of Co/SiO₂Magnetic Nanocomposites

Radchenko

Lashkarev

Baibara

et al. 2019

Physica Status Solidi (b)

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Electric, thermoelectric, and magnetic properties of the magnetic nanocomposite (MNC) Co/SiO2 consisting of nanometer‐size Co nanoparticles embedded in SiO2 dielectric matrix have been studied. MNC is obtained in the form of (0.8–2.3) μm thick films with Co concentration 31.7–65.4 at.% by the electron beam physical vapor deposition method on polycrystalline Al2O3 substrates. The temperature dependence of the resistivity follows the Mott law. The negative magnetothermoelectric power discovered in MNC Co/SiO2 can be explained by hopping conductivity through the magnetic localization centers in the SiO2 matrix or chemical interaction of Co with Si and O2, which results in a mixture of CoSi (ferromagnetic) and CoO (antiferromagnetic) phases. As the cobalt concentration increases, the particle size increases and the interparticle distances decrease. This is confirmed by the magnetic behavior of the sample with high Co concentration, which is dominated by large Co nanoparticles and strong interparticle magnetic interactions.

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“…www.nature.com/scientificreports www.nature.com/scientificreports/ fcc cobalt. Ii is well known 39,40,42,43 that in addition to hcp cobalt nanoparticles, cobalt nanoparticles with fcc crystal structure can also be found in the experiment. For completeness, we calculate single-domain diameters for cobalt nanoparticles with fcc crystal structure having cubic type of magnetic anisotropy.…”

Section: Two Domain Configurationmentioning

confidence: 88%

Multi-domain structures in spheroidal Co nanoparticles

Usov

Nesmeyanov

2020

Sci Rep

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Multi-domain structures in spheroidal co nanoparticles n. A. Usov 1,2 ✉ & M. S. nesmeyanov 2 the structure of multi-domain micromagnetic states in hcp cobalt nanoparticles of spheroidal shape has been studied using numerical simulation in the range of diameters 20-200 nm. The single-domain diameters of the particles are determined depending on their aspect ratio. the complicated vortex structure of domain walls for two-and three-domain micromagnetic configurations is investigated. it has been shown that three domain states are actually strongly deformed two vortex states. in hcp cobalt particles of sufficiently large sizes two types of three-domain micromagnetic states with close total energies have been obtained. They differ in different magnetization directions of the exchange cores of the vortex domain walls. The remanent magnetization of particles has been calculated for twoand three-domain micromagnetic states. the single-domain diameters of fcc cobalt nanoparticles with cubic type of magnetic anisotropy were also calculated. Cobalt nanoparticles attract substantial interest due to their technological significance 1. They were also the first magnetic nanoparticles extensively studied theoretically 2-5. However, the theory of small magnetic particles developed by Kittel 2 , Stoner and Wohlfarth 3 , Brown 4 , and Aharoni 5 is only capable to describe the magnetic properties of single-domain nanoparticles. Meanwhile, magnetic nanoparticles of submicron sizes are often found in practice. For example, the assemblies of magnetic nanoparticles with a wide size distribution are frequently obtained in chemical synthesis 6 , so that the sizes of some particles may exceed the corresponding single domain diameter. Particles of sufficiently large sizes can arise during prolonged annealing of thin-film samples 7 , they can be created as a result of implantation process 8 , etc. It is worth noting that the magnetic properties of submicron-sized nanoparticles play an important role in paleo-magnetism 9. The magnetic properties of nanoparticles in inhomogeneous micromagnetic states differ significantly from those of single-domain ones 1,4,5. However, the characteristics of nanoparticles of sufficiently large sizes are still poorly investigated. In particular, the dependence of the single-domain diameter of a spheroidal cobalt nanoparticle on its aspect ratio is unknown. The upper and lower analytical estimates for the single-domain diameter of magnetic nanoparticle given by Brown 10 are not always close enough. Therefore, in most cases a detailed numerical simulation is necessary to determine the single-domain diameter of particles of various magnetic materials. At present, domain structures in submicron cobalt nanoparticles and cobalt nanowires are experimentally studied using magnetic force microscopy 11,12. In addition, modern electronic holography technique 13-17 allows to study experimentally inhomogeneous micromagnetic distributions in magnetic nanoparticles and nanowires. This revives interest in detailed micromagneti...

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Size effects of the magnetic anisotropy of fcc cobalt nanoparticles embedded in copper

Cited by 9 publications

References 19 publications

Emergent magnetism and exchange bias effect in iron oxide nanocubes with tunable phase and size

Emergent magnetism and exchange bias effect in iron oxide nanocubes with tunable phase and size

Electronic Transport and Magnetic Properties of Co/SiO₂Magnetic Nanocomposites

Multi-domain structures in spheroidal Co nanoparticles

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Size effects of the magnetic anisotropy of fcc cobalt nanoparticles embedded in copper

Cited by 9 publications

References 19 publications

Emergent magnetism and exchange bias effect in iron oxide nanocubes with tunable phase and size

Emergent magnetism and exchange bias effect in iron oxide nanocubes with tunable phase and size

Electronic Transport and Magnetic Properties of Co/SiO2Magnetic Nanocomposites

Multi-domain structures in spheroidal Co nanoparticles

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Electronic Transport and Magnetic Properties of Co/SiO₂Magnetic Nanocomposites