We mechanically exfoliate mono- and few-layers of the transition metal dichalcogenides molybdenum disulfide, molybdenum diselenide, and tungsten diselenide. The exact number of layers is unambiguously determined by atomic force microscopy and high-resolution Raman spectroscopy. Strong photoluminescence emission is caused by the transition from an indirect band gap semiconductor of bulk material to a direct band gap semiconductor in atomically thin form.

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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...

All-optical switching (AOS) in ferrimagnetic Fe(100-x)Tb(x) alloys is presented. AOS is witnessed below, above, and in samples without a magnetic compensation point. It is found that AOS is associated with laser heating up to the Curie temperature and intimately linked to a low remanent sample magnetization. Above a threshold magnetization of 220 emu/cc helicity dependent AOS is replaced by pure thermal demagnetization.

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