Karl Franzens University Graz
Graz University of Technology
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Karl Franzens University Graz | Graz University of Technology | |
Magnetic nanostructures for data storage and sensor technology This talk focuses on two important application of magnetic nanostructures. The first part of the talk deals with magnetic storage concepts that support ultra high storage densities. In order to further increase the storage capacity one has to break the recording dilemma, which means that it is usually assumed that it is not possible to get small magnetic grains that are thermally stable but easy to switch. A new type of media so called exchange spring and graded media is discussed which recently was applied to state of the art commercial hard discs. Furthermore concept of 3-D recording, where multiple layers are addressed independently is discussed. The basic idea relies on using microwave fields or currents to switch independent magnetic layers. In the second part of the talk the potential of magneto elastic sensors is discussed which can be used to remotely measure a variety of physical and chemical properties such as stress, temperature, PH concentrations, fluid-flow velocity humidity. The basic principle of these sensors bases on a magnetostrictive ribbon which is subjected to a magnetic field. Due to the effect of magnetostriction the magnetic field mechanically deforms the magnetic ribbon. After switching off the field the sensor start to oscillate mechanically until the equilibrium length is finally reached again. The inverse effect of magnetostriction (Villari effect) transforms the mechanical oscillation into an ac magnetic field, which can be detected with induction coils. The application of this sensor concept to measure temperature and stress will be discussed in detail. |