Magnetic studies on mass-selected iron particles

Methling, Ralf; Senz, Volkmar; Klinkenberg, E.-D.; Diederich, Th.; Tiggesbäumker, J.; Holzhüter, G.; Bansmann, Joachim; Meiwes‐Broer, Karl‐Heinz

doi:10.1007/s100530170085

Cited by 66 publications

(50 citation statements)

References 8 publications

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“…The wafers are annealed in the UHV RHEED system (base pressure: 5 × 10 −9 mbar) at a temperature of about 525 K until the pressure in the chamber recovers (after an initial increase) and the recorded RHEED pattern indicates a clean and flat SiO x surface. (iii) Finally, the nanoparticles are deposited onto the prepared substrates using an arc cluster ion source (ACIS), which is attached to the SPS [43][44][45]. For RHEED and X-PEEM investigations, all samples are transferred under UHV conditions.…”

Section: Methodsmentioning

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: Methodsmentioning

confidence: 99%

“…In the ACIS, the nanoparticles are formed by condensation of metal vapor in a carrier gas consisting of a He/Ar mixture [43]. The metal vapor is generated by means of arc erosion of respective metal targets with a purity of 99.8%.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2017

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“…In order to realise this potential and produce commercial devices that incorporate nanosized particles, an important first step is to develop the ability to prepare macroscopic samples, which contain the nanoparticles of interest embedded in a matrix of a different material. A range of techniques have been used to prepare such cluster-assembled materials, but the most flexible is a co-deposition technique involving the use of a cluster source, as used by various groups [1][2][3]. As described in more detail in the following section, this technique produces films in which there is a high degree of control over the nanostructure.…”

Section: Introductionmentioning

confidence: 99%

Extended x-ray absorption fine structure studies of the atomic structure of nanoparticles in different metallic matrices

Baker¹,

Roy

Gurman

et al. 2009

J. Phys.: Condens. Matter

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It has been appreciated for some time that the novel properties of particles in the size range 1 -10 nm are potentially exploitable in a range of applications. In order to ultimately produce commercial devices containing nanosized particles, it is necessary to develop controllable means of incorporating them into macroscopic samples. One way of doing this is to embed the nanoparticles in a matrix of a different material, by co-deposition for example, to form a nanocomposite film. The atomic structure of the embedded particles can be strongly influenced by the matrix. Since some of the key properties of materials, including magnetism, strongly depend on atomic structure the ability to determine atomic structure in embedded nanoparticles is therefore very important. This review focuses on nanoparticles, in particular magnetic nanoparticles, embedded in different metal matrices. EXAFS provides an excellent means of probing atomic structure in nanocomposite materials, and an overview of the technique is given. Its application to catalytic metal clusters is described briefly, before giving an account of the use of EXAFS in determining atomic structure in magnetic nanocomposite films. In particular, we focus on cluster-assembled films comprised of Fe and Co nanosized particles embedded in various metal matrices, and show how the crystal structure of the particles can be changed by appropriate choice of matrix material. The work discussed here demonstrates that combining the results of structural and magnetic measurements, as well as theoretical calculations, can play a significant part in tailoring the properties of new magnetic cluster-assembled materials.

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“…Both the pure supersonic expansion and the seeded coexpansion sources produce metal clusters that are hot; in fact, they remain liquid during their entire journey through the molecular beam apparatus [15]. To date, Fe clusters have mostly been produced using gas aggregation sources in which the Fe is evaporated using either lasers [16], thermal heating [17] or arc erosion [18]. A notable exception is the supersonic source reported in [19] which works using the seed gas-co-expansion principle.…”

Section: Introductionmentioning

confidence: 99%

Production of Fe clusters by collisions of metal vapour with supersonic argon beams

Akraiam

Haeften

2013

Eur. Phys. J. D

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Abstract. The growth of Fe clusters by collisions of Fe atoms with Ar atoms flowing in a supersonic beam was investigated by Fe mass flux measurements and transmission electron (TEM) microscopy. Moderate Ar densities of the order of 1×10 20 m −3 were sufficient to cause cluster growth which was attributed to the low temperature of the Ar beam. TEM imaging of deposited clusters revealed diameter distributions from 2 to 10 nm depending on the deposition time. Extrapolation to zero deposition time revealed a cluster size of 2.4 nm grown in the gas phase. Growth on the surface was attributed to diffusion of single Fe atoms which are co-deposited with the clusters in the process and which agglomerate when they hit a cluster.

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Magnetic studies on mass-selected iron particles

Cited by 66 publications

References 8 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

Extended x-ray absorption fine structure studies of the atomic structure of nanoparticles in different metallic matrices

Production of Fe clusters by collisions of metal vapour with supersonic argon beams

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