ExperimentalCharacterization: The UV-visible spectra were recorded on a Shimadzu 3101 spectrophotometer. Dynamic light scattering studies were carried out using a Horiba LB-550 instrument. Transmission electron micrographs of the clusters were recorded by applying a drop of the sample to a carbon-coated copper grid (JEOL JEM-200CX). AFM measurements were obtained using a Digital Nanoscope III in the tapping mode.Photoelectrochemical Measurements: The photoelectrochemical measurements were performed in a one-compartment Pyrex UV cell with a standard three electrode arrangement consisting of a working electrode, a Pt wire counter electrode, and a Ag/AgNO 3 reference electrode (0.5 M LiI and 0.01 M I 2 in acetonitrile as the electrolyte). Photocurrent measurements were made with an ALS 630A electrochemical analyzer. Monochromatic light obtained by passing light from a 500 W xenon lamp (Ushio XB-50101AA-A) through a monochromator (Ritsu MC-10N) was used for excitation.

One of the most challenging issues in the characterization of magnetic materials is to obtain quantitative analysis on the nanometer scale. Here we describe how electron magnetic circular dichroism (EMCD) measurements using the transmission electron microscope (TEM) can be used for that purpose, utilizing reciprocal space maps. Applying the EMCD sum rules, an orbital to spin moment ratio of mL/mS = 0.08 ± 0.01 is obtained for Fe, which is consistent with the commonly accepted value. Hence, we establish EMCD as a quantitative element specific technique for magnetic studies, using a widely available instrument with superior spatial resolution.PACS numbers: 68.37. Lp, 75.70.Ak, 78.20.Bh, 79.20.Uv Keywords: magnetic circular dichroism, electron energy-loss spectra, transmission electron microscopy Fast advances in the field of magnetic nanostructures, both in fundamental research and technological development, call for new magnetic characterization methods. Electron microscopy is nowadays a standard technique for structural and chemical analysis down to the atomic scale. Magnetic imaging [1] in the TEM is also possible while measurements of element-specific magnetic moments have until now been the domain of synchrotron based dichroic experiments, such as x-ray magnetic circular dichroism (XMCD) [2]. Although XMCD is widely applied in materials science, it is mainly related to surface measurements and with limitations in spatial resolution. The work of Schattschneider et al.[3] -reporting an observation of dichroic effects in the TEM -opened a new route for high-resolution element specific magnetic characterization, using widely accessible standard laboratory equipment.EMCD measurements are in principle simple. An unpolarized electron beam, passing through a magnetic material, exhibits a magnetic dichroism in the momentum resolved electron energy-loss spectra (EELS) [3]. The origin of this effect stems from the inelastic scattering of incoming high-energy electrons that excite core electrons to unoccupied states. The signal at a scattering vector k contains mixed contributions of all pairs of diffracted beams with momentum transfers q and q . A dichroic effect appears when two EELS-spectra -extracted at specific detector positions in reciprocal space defined by a mirror axis -are subtracted (see Fig. 1). This difference spectrum is called in the following the EMCD signal.While the principle of EMCD has been demonstrated, decisive progress is required to allow quantitative magnetic analysis, which is reported here. The recent derivation of the EMCD sum rules for extraction of spin (m S ) and orbital (m L ) magnetic moments represents an important step in that direction [4,5]. As EMCD relies on reciprocal space vectors, proper k-space selection of detector positions is essential. So far, most measurements are carried out by selecting a limited part of reciprocal space from where the EELS-spectra are acquired [3,6]. As shown in this letter, increased flexibility for data optimization and precision in k-space selection i...

Magnetic multilayered, onion-like, heterostructured nanoparticles are interesting model systems for studying magnetic exchange coupling phenomena. In this work, we synthesized heterostructured magnetic nanoparticles composed of two, three, or four components using iron oxide seeds for the subsequent deposition of manganese oxide. The MnO layer was allowed either to passivate fully in air to form an outer layer of Mn(3)O(4) or to oxidize partially to form MnO|Mn(3)O(4) double layers. Through control of the degree of passivation of the seeds, particles with up to four different magnetic layers can be obtained (i.e., FeO|Fe(3)O(4)|MnO|Mn(3)O(4)). Magnetic characterization of the samples confirmed the presence of the different magnetic layers.

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We demonstrate how layer specific in-plane magnetic anisotropy can be imprinted in amorphous multilayers. The anisotropy is obtained by growing the magnetic layers in the presence of an external field and the anisotropy direction can thereby be arbitrarily chosen for each of the magnetic layers. We used Co68Fe24Zr8 and Al70Zr30 layers as building blocks for demonstrating this effect. The imprinting is expected to be obtainable for a wide range of amorphous materials when grown at temperatures below the magnetic ordering temperature.

Electron magnetic chiral dichroism (EMCD) is an emerging tool for quantitative measurements of magnetic properties using the transmission electron microscope (TEM), with the possibility of nanometer resolution. The geometrical conditions, data treatment and electron gun settings are found to influence the EMCD signal. In this article, particular care is taken to obtain a reliable quantitative measurement of the ratio of orbital to spin magnetic moment using energy filtered diffraction patterns. For this purpose, we describe a method for data treatment, normalization and selection of mirror axis. The experimental results are supported by theoretical simulations based on dynamical diffraction and density functional theory. Special settings of the electron gun, so called telefocus mode, enable a higher intensity of the electron beam, as well as a reduction of the influence from artifacts on the signal. Using these settings, we demonstrate the principle of acquiring real space maps of the EMCD signal. This enables advanced characterization of magnetic materials with superior spatial resolution.

The structural properties of a tetragonally distorted Fe 1−x Co x alloy, in the form of Fe 1−x Co x /Pt(001) superlattices with x = 0.64, have been investigated experimentally. The study follows recent theoretical predictions on the enhanced uniaxial magnetocrystalline anisotropy of such alloys with specific combinations of chemical composition and tetragonal distortion. The ratio between out-of-plane and in-plane lattice parameters in the Fe 0.36 Co 0.64 layers, c/a, was found to vary between 1.18 and 1.31, depending on the thickness ratio between the alloy and the spacer. This covered the range of interest c/a = 1.20-1.25 in the previous calculations and should be compared to c/a = 1 in the original bcc alloy lattice. Simulations of x-ray diffraction patterns as well as density functional calculations support the derivation of the Fe 0.36 Co 0.64 lattice parameters.

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