Fyzikální ústav Akademie věd ČR

Selected results of department 11

Highly anisotropic f-electron magnets

The rare earth (4f) intermetallic compounds with Fe or Co are famous as extremely powerful permanent magnets with exceptionally high uniaxial magneto-crystalline anisotropy. In R2Co17 compounds (R is a rare-earth metal), the strongest interaction is the Co-Co exchange interaction which primarily determines their Curie temperature, TC.  The full text >>

Exchange bias in UO2/Fe3O4 thin films

The exchange interaction through interface of dissimilarly ordered magnetic materials (e.g. an antiferromagnet (AF) in contact with a ferro- or ferrimagnet (F)) gives rise to a characteristic exchange bias (EB) effect [1] (i.e. shifted magnetic hysteresis loop with an enhanced coercivity), which is of fundamental importance for novel hard magnets, recording media, spin valve and tunneling devices.  The full text >>

Fundamental properties of superfluidity: electrical activity of He II studied with second-sound

The electrical activity of superfluid 4He induced by the relative motion of normal and superfluid components has been recently observed. It was induced in two different types of experiments. In a first experiment the electric potential oscillations were generated by a wave of second-sound, the out-of-phase oscillation of the normal and superfluid components. In a second experiment liquid helium was involved in motion by a torsional oscillator whose walls affected the normal component only.  The full text >>

Quantum turbulence: pure superflow through channels

We are studying experimentally the turbulent state of bellows-driven 4He superfluid flows in channels. Turbulence in a superfluid takes the form of a tangle of atomically-thin vortex lines with quantized velocity circulation, which arise as a consequence of the Bose-Einstein condensation of the superfluid [1]. In one project [2-4] we have studied the dependence of the total length of vortex lines, L, with mean flow velocity, v, in conditions of steady-state turbulence.  The full text >>

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