Incidence of the Brownian Relaxation Process on the Magnetic Properties of Ferrofluids.

Ferrofluids containing magnetic nanoparticles represent a special class of magnetic materials due to the added freedom of particle tumbling in the fluids. We studied this process, known as Brownian relaxation, and its effect on the magnetic properties of ferrofluids with controlled magnetite nanoparticle sizes. For small nanoparticles (below 10 nm diameter), the Néel process is expected to dominate the magnetic response, whereas for larger particles, Brownian relaxation becomes important.

Impedance Spectroscopy of Encapsulated Single Graphene Layers.

In this work, we demonstrate the use of electrical impedance spectroscopy (EIS) for the disentanglement of several dielectric contributions in encapsulated single graphene layers. The dielectric data strongly vary qualitatively with the nominal graphene resistance. In the case of sufficiently low resistance of the graphene layers, the dielectric spectra are dominated by inductive contributions, which allow for disentanglement of the electrode/graphene interface resistance from the intrinsic graphene resistance by the application of an adequate equivalent circuit model.

Metastable Materials Accessed under Moderate Pressure Conditions (P ≤ 3.5 GPa) in a Piston-Cylinder Press.

In this review, we describe different families of metastable materials, some of them with relevant technological applications, which can be stabilized at moderate pressures 2-3.5 GPa in a piston-cylinder press. The synthesis of some of these systems had been previously reported under higher hydrostatic pressures (6-10 GPa), but can be accessed under milder conditions in combination with reactive precursors prepared by soft-chemistry techniques.

Influence of Nanostructuration on PbTe Alloys Synthesized by Arc-Melting.

PbTe-based alloys have the best thermoelectric properties for intermediate temperature applications (500-900 K). We report on the preparation of pristine PbTe and two doped derivatives (PbSbTe and AgSbPbTe, so-called LAST18) by a fast arc-melting technique, yielding nanostructured polycrystalline pellets. XRD and neutron powder diffraction (NPD) data assessed the a slight Te deficiency for PbTe, also yielding trends on the displacement factors of the 4 and 4 sites of the cubic space group.

Signatures of a two-dimensional ferromagnetic electron gas at the La0.7Sr0.3MnO3/SrTiO3 interface arising from orbital reconstruction.

The magnetoresistance of La0.7Sr0.3MnO3/SrTiO3 superlattices with magnetic field rotating out-of-plane shows unexpected peaks for in-plane fields.