Luca Martino

Fluxmetric-magnetooptical approach to broadband energy losses in amorphous ribbons

The magnetization process in field annealed amorphous ribbons has been investigated from dc to 10 MHz. Loss and permeability measurements, carried out both on single strips and ring samples by means of a broadband fluxmetric setup, have been associated with observations of the domain wall dynamics by high-speed stroboscopic Kerr apparatus. Transverse anisotropy Co-based ribbons exhibit a combination of rotational and domain wall processes, the latter being observed to progressively damp with frequency and coming to a halt on approaching the megahertz range. Given the vanishing direct contribution of the domain walls to the high-frequency magnetization process, the so-called classical loss formulation, associated with the rotational magnetization processes, is expected to correspondingly hold for the energy loss W(f). Under these conditions, W(f) tends to increase linearly with f, which, in view of the expected surge of the skin effect, does not agree with the f1/2 behavior accordingly predicted by standar...

Fabrication of new Magnetic Micro-Machines for minimally invasive surgery

Magnetic micro-machines (MMM) have been proposed as effective tools for minimally invasive surgery. An innovative and low cost MMM manufacturing process, based on casting of a mixture of SmCo powders and acrylic resin into silicone moulds, is presented. A MMM prototype has been manufactured with this new process and its swimming ability tested by using different siliconic oils of known kinematic viscosity. The propulsion efficiency, given by the velocity and frequency ratio, has been found comparable with other MMM reported in the literature.

Fabrication of New Magnetic Micro-Machines for Minimally Invasive Surgery

Magnetic micro-machines (MMM) have been proposed as effective tools for minimally invasive surgery. An innovative and low cost MMM manufacturing process, based on casting of a mixture of SmCo powders and acrylic resin into silicone moulds, is presented. A MMM prototype has been manufactured with this new process and its swimming ability tested by using different siliconic oils of known kinematic viscosity. The propulsion efficiency, given by the velocity and frequency ratio, has been found comparable with other MMM reported in the literature.

Magnetocaloric Properties of MnBi Compound as a Function of Grain Size

MnBi is a magnetic material with many peculiar properties, interesting for different applications such as rare-earth-free permanent magnets and magnetic refrigeration. In this work the entropy change and the transformation kinetics of the magneto-structural transition are investigated, for two sets of samples with different grain size (“as-annealed” and “compacted pwd”). Both sets show a logarithm dependence on the temperature scan rate of the transition temperature upon cooling. This suggests that thermal activation effects are present. The estimated activation volume v0 of the magneto-structural transition corresponds to around 120 atoms.