Structure and magnetic moments of mass-filtered deposited nanoparticles

Kleibert, Armin; Passig, Johannes; Meiwes‐Broer, Karl‐Heinz; Getzlaff, M.; Bansmann, Joachim

doi:10.1063/1.2745330

Cited by 59 publications

(59 citation statements)

References 36 publications

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“…This is surprising since theory treats a perfect monolayer, whereas the XMCD measurements have been performed on granular films. 53 and a significantly smaller one for 6-ML-thick FeCo films on Rh͑100͒ close to the equiatomic composition ͑1.8 B ͒. 7 An evident discrepancy between theory and XMCD data exists in the case of pure Fe for which we measured a strongly reduced effective spin moment of S eff = ͑1.2Ϯ 0.2͒ B vs 3.0 B found by theory.…”

Section: A Experiments Versus Theorymentioning

confidence: 56%

High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

et al. 2008

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The magnetism of 1-ML-thick films of Fe x Co 1−x on Pt͑111͒ was investigated both experimentally, by x-ray magnetic circular dichroism and magneto-optical Kerr effect measurements, and theoretically, by firstprinciples electronic structure calculations, as a function of the film chemical composition. The calculated Fe and Co spin moments are only weakly dependent on the composition and close to 3 B / atom and 2 B / atom, respectively. This trend is also seen in the experimental data, except for pure Fe, where an effective spin moment of only S eff = ͑1.2Ϯ 0.2͒ B / atom was measured. On the other hand, both the orbital moment and the magnetic anisotropy energy show a strong composition dependence with maxima close to the Fe 0.5 Co 0.5 stoichiometry. The experiment, in agreement with theory, gives a maximum magnetic anisotropy energy of 0.5 meV/atom, which is more than 2 orders of magnitude larger than the value observed in bulk bcc FeCo and close to that observed for the L1 0 phase of FePt. The calculations clearly demonstrate that this composition dependence is the result of a fine tuning in the occupation number of the d x 2 −y 2 and d xy orbitals due to the Fe-Co electronic hybridization.

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Section: A Experiments Versus Theorymentioning

confidence: 56%

High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

et al. 2008

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“…For the present paper, the cluster source operation parameters as well as the mass-filter settings are held constant for all samples. This ensures similar growth, selection, and landing conditions in all experiments, with the kinetic energy of the particles prior to the impact on the substrate smaller than 0.1 eV/atom [44]. With these settings, the deposition takes place under so-called soft landing conditions, where no fragmentation of the particles or damage to the substrate is expected [46,47].…”

Section: Methodsmentioning

confidence: 99%

“…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%

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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“…1,2,8 The present monodispersed silver clusters were produced using an arc cluster ion source. 9 The subsequent mass separation of the desired cluster size was achieved by an electrostatic quadrupole deflector. As support material, a 3 ML ͑monolayer͒ thick amorphous alumina film prepared by atomic layer deposition on the top of a naturally oxidized silicon wafer was used.…”

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confidence: 99%