|
|
Low temperature part of penetration depth in conventional and unconventional superconductors
Baničová, Lucia ; Janů, Zdeněk (advisor) ; Havela, Ladislav (referee)
In the present work I study temperature dependence of magnetic penetration depth in superconductors which allows us to determine the symetry of the order parameter, important for theoretical models. In conventional superconductors we talk about s-symetry. Energy gap is isotropic and as a consequence of this fact penetration depth grows exponencialy with the temperature. On the other hand, in unconventional superconductors with d-symetry we find the power dependence on the temperature. Anyway the exponent depends on impurities and structure of the material and the influence of these parametrs is not completely clear at the moment.
|
|
|
Temperature dependence of susceptibility of thin Pb films
Truněček, Otakar ; Janů, Zdeněk (advisor) ; Vašek, Petr (referee)
This master thesis is focused on temperature dependence of magnetization curves and susceptibility of thin films of type-I superconductor. A model for susceptibility of type-I superconductor in intermediate state is presented. This model is compared with experimental data yielding temperature dependence of critical magnetic field of superconductor. Furthermore it is shown that sufficiently thin film of superconductor which is type-I in bulk can exhibit type-II behaviour in perpendicular magnetic field. Susceptibility measured on such a film is therefore compared to susceptibility calculated for Bean model for type-I superconductors.
|
|
| |
|
| |
|
| |
|
| |
|
| |
|
|
Kritický stav v tenkém Nb filmu
Youssef, A.E. ; Švindrych, Z. ; Hadač, J. ; Janů, Zdeněk
We present high resolution measurements of temperature dependence of low frequency ac magnetic susceptibility of superconducting Nb thin film in perpendicular time-varying periodic applied magnetic fields. We map this data, including harmonics, to the ac susceptibility calculated on basis of the complete analytical model of magnetization of thin superconducting disk in critical state. We find an excellent agreement between the measured and model data for temperatures up to 0.9997Tc
|
|
|
Magnetická studia fázových přechodů v magnetitu
Švindrych, Z. ; Janů, Zdeněk ; Hadač, J.
We have measured low field dc and low frequency ac magnetic properties of high quality magnetite single crystals with continuously reading high resolution SQUID magnetometer in a temperature range of 5 – 150 K. In these data several features can be observed: the anisotropy point around 130 K, Verwey transition near 122 K, glass-like transition around 40 K and finally anomalous magnetic behaviour at lowest temperatures (below 30 K).
|
guest ::
