Merry Christmas and a Happy New Year!

OOMMF simulation

The VIARAM team wishes Merry Christmas and a Happy New Year to all colleagues and readers of our blog. We are looking forward to further discuss with you here or in real, e.g. on the DPG spring conferences in Wuppertal and Berlin (March 2015), and to exchange ideas and inspiration regarding advanced materials.

See you in 2015!

Design of active magneto-optic elements

While macroscopic passive magneto-optic devices, such as polarization rotators, are common optical components used in a variety of experiments, nano-scale active magneto-optic elements are an important part of quantum information transport. Plasmon resonances (light induced collective electron oscillations) can be used to tailor the Kerr rotation and ellipticity in a broad range, up to controlled sign changes.

Overview of Origami-inspired active structures

The combination of active materials with Origami-inspired folding techniques results in self-folding or -unfolding structures. Such active materials can fold / unfold parts by changing their length, bending or resetting their preset folded shape. Possible active materials are, amongst others, shape memory allows, shape memory polymers, ionic electro-active polymers, or piezoelectric ceramics and polymers, depending on the desired application. Materials can be activated thermally, chemically, optically, electrically, or magnetically.

Overview of thermal sensors measuring the heat flux through the human body

In the development of thermal protective performance (TPP) clothing for firefighters and industrial workers it is necessary to have sensors which simulate and predict the heat flux through a human body exposed to fire. Several geometries are used to build these sensors, such as embedded thermo-couples, surface-mounted thermo-couples, a full-scale manikin with thermocouples, or a water-cooled sensor used for calibration purposes.

Structured exchange bias systems for multidigit storage systems

The technical and physical limits of the bit feature size in hard disk drives led to the question whether to realize multidigit memories with more than 1 bit (two possible states) per storage position. A new approach to realize a multidigit memory has been published by Morales et al. who show that an exchange bias system can exhibit five and more different states at remanence, depending on the cooling field.

Collective magnetic properties of iron oxide nanoparticle-clusters

Block copolymers can be used as “containers” which can be filled, e.g., by drugs, dyes, nanoparticles etc. Such polymeric containers can also contain ordered clusters of nanoparticles – with possibly novel collective properties, different from those of single nanoparticles and bulk material.

In a recent study, FeO_x nanoparticles of diameter 8 nm were encapsulated in such a block copolymer with ratios of polymer:nanoparticle between 20:1 and 400:1. Additionally, hybrid nanomaterials combining FeO_x with quantum dots, quantum rods, gold nanoparticles etc. were produced.

MagCalc 1.0 online

The first version of the spreadsheet-based hysteresis calculation programm MagCalc 1.0 can be found in the download area.

Feel free to add your comments here - do you need any special program version for teaching or research? Let us know, and we will try our best to create what you need.

Room temperature exchange bias in Mn3Ge

Polycrystalline Mn3Ge ingots, synthesized by repeated inductive melting, show an exchange bias (EB) up to room temperature. This unidirectional anisotropy leads to a vertical shift of the hysteresis loop. Additionally, typical features of EB systems, such as the training effect (resulting in reduced EB values for repeated hysteresis loops after a field cooling process) or the up-shift of the loops (which is explained by the Domain State Model), are clearly visible.

Beyond graphene

Today graphene is widely known as a prototypical two-dimensional material possessing special physical properties. Two-dimensionality of different monolayer materials can lead, however, to new, extraordinary properties.

Researches from Chemnitz Technical University (Germany) and Nanyang Technological University (Singapore) prepared MoS2, MoSe2, and WSe2 monolayers overcoming the difficulty of creating an optical bandgap in graphene.

Electrodeposited magnetic nanowires

One-dimensional magnetic nano-materials – such as nanowires and nanotubes – are of special interest for the development of sensors and devices. Additionally, they can give rise to basic physical questions, regarding magnetization reversal processes in these special shapes.

Magnetic nanowires can be deposited, e.g., by electrochemical deposition. Co-Pt nanowires are of special interest for several applications due to their expected strong magneto-crystalline anisotropy. Magnetization can be probed in such nanowires using magnetic force microscopy (MFM).