Ferromagnetic Stability in Fe Nanodot Assemblies on Cu(111) Induced by Indirect Coupling through the Substrate

Pierce, J. P.; Torija, M. A.; Gai, Zheng; Shi, Junren; Schulthess, T. C.; Farnan, G. A.; Wendelken, J. F.; Plummer, E. W.; Shen, Jian

doi:10.1103/physrevlett.92.237201

Cited by 63 publications

(77 citation statements)

References 17 publications

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“…Instead, the available literature reveals a significant scatter of magnetic properties that cannot be assigned only to particle size or environment. For instance, the magnetic anisotropy energies of Fe nanoparticles are reported to range from bulklike to * Corresponding author: armin.kleibert@psi.ch strongly enhanced values in different experiments [13][14][15][16][17][18][19]. Similarly, for Co nanoparticles the experimentally observed values vary over several orders of magnitude [20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…For Ni, the situation seems even more complex, since not only does the magnetic anisotropy energy vary, but also the magnetic moment of the particles differs in various reports [26][27][28][29][30][31][32]. Such variability is often assigned to shape, surface, or interface effects [18,22,33]. However, an unambiguous interpretation of the experimental data is difficult, since most of the reported investigations have been carried out with experimental techniques that average over large distributions of particle sizes, morphologies, and orientations.…”

Section: Introductionmentioning

confidence: 99%

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Direct observation of enhanced magnetism in individual size- and shape-selected 3d transition metal nanoparticles

et al. 2017

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Magnetic nanoparticles are critical building blocks for future technologies ranging from nanomedicine to spintronics. Many related applications require nanoparticles with tailored magnetic properties. However, despite significant efforts undertaken towards this goal, a broad and poorly understood dispersion of magnetic properties is reported, even within monodisperse samples of the canonical ferromagnetic 3d transition metals. We address this issue by investigating the magnetism of a large number of size-and shape-selected, individual nanoparticles of Fe, Co, and Ni using a unique set of complementary characterization techniques. At room temperature, only superparamagnetic behavior is observed in our experiments for all Ni nanoparticles within the investigated sizes, which range from 8 to 20 nm. However, Fe and Co nanoparticles can exist in two distinct magnetic states at any size in this range: (i) a superparamagnetic state, as expected from the bulk and surface anisotropies known for the respective materials and as observed for Ni, and (ii) a state with unexpected stable magnetization at room temperature. This striking state is assigned to significant modifications of the magnetic properties arising from metastable lattice defects in the core of the nanoparticles, as concluded by calculations and atomic structural characterization. Also related with the structural defects, we find that the magnetic state of Fe and Co nanoparticles can be tuned by thermal treatment enabling one to tailor their magnetic properties for applications. This paper demonstrates the importance of complementary single particle investigations for a better understanding of nanoparticle magnetism and for full exploration of their potential for applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Direct observation of enhanced magnetism in individual size- and shape-selected 3d transition metal nanoparticles

et al. 2017

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“…Today in physics new phenomena and applications continue to emerge; recent investigations have uncovered metastable ferromagnetic states measured in individual nanoparticles [4], surface mediated particle interactions and anisotropy [5][6][7], interactions in arrays of patterned nanoislands known as artificial spin ice [8][9][10] and applications related to hyperthermia-based medical treatments [11]. There remain many fascinating questions to be answered, particularly regarding particle ensembles with interaction forces present.…”

Section: Introductionmentioning

confidence: 99%

Ensemble magnetic behavior of interacting CoFe nanoparticles

et al. 2015

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Ferromagnetic nanoparticles in the 10-14 nm size range are examined for their size and interaction dependent magnetic properties. From X-ray magnetic circular dichroism the orbital-to-spin magnetic moment ratio is determined and found to decrease significantly with particle size. This is in accordance with previous complementary studies on smaller particles and highlights the difficulty of fitting to a simple core-shell model. Vibrating sample magnetometry experiments on samples with more than 1000 particles per square micron show a wide distribution of blocking temperatures from 50 to greater than 650 K. This is attributed to the dipole-dipole magnetic coupling forces between particles. The blocking temperatures show an unexpected negative correlation with increasing particle density.

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“…4,13 However, a different situation is encountered in exchange-enhanced Pauli paramagnets, such as Pt and Pd. These metals are close to the onset of ferromagnetism, which translates into an extra exchange contribution.…”

Section: Preasymptotic Couplingmentioning

confidence: 99%

Substrate-controlled growth and magnetism of nanosize Fe clusters on Pt

Skomski

Zhang

Sessi

et al. 2008

Journal of Applied Physics

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The growth and magnetism of nanosize Fe clusters on Pt and other metal surfaces are investigated. Fe clusters have been fabricated directly on the substrates by buffer layer assisted growth under ultrahigh vacuum conditions. The mean cluster diameter and the average cluster spacing were controlled by the Fe coverage and the buffer layer thickness. The enhanced magnetic anisotropy of such clusters of diameters between 0.5 and 10 nm with respect to bulk is discussed. Interface anisotropy contributions are compared with direct dipolar cluster-cluster interaction and indirect interactions mediated by the substrate, including preasymptotic ferromagnetic interaction. It is found that this preasymptotic exchange is rather strong in exchange-enhanced substrates, such as Pt, but it decreases rapidly with increasing distance between clusters and becomes negligible for the experimental cluster spacings in this work. Except for clusters that nearly touch each other, the leading interaction contributions are RKKY-type exchange and magnetostatic dipole interactions.

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Ferromagnetic Stability in Fe Nanodot Assemblies on Cu(111) Induced by Indirect Coupling through the Substrate

Cited by 63 publications

References 17 publications

Direct observation of enhanced magnetism in individual size- and shape-selected 3d transition metal nanoparticles

Direct observation of enhanced magnetism in individual size- and shape-selected 3d transition metal nanoparticles

Ensemble magnetic behavior of interacting CoFe nanoparticles

Substrate-controlled growth and magnetism of nanosize Fe clusters on Pt

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