636 research outputs found
Mixed state Hall effect in the multiphase superconductors
Hall effect below Tc in multiphase superconductors has been studied on
Bi-based superconductors. Samples with different relative content of 2212 and
2223 phase have been prepared. The phase content has been verified by X-ray
diffraction. Results show that while resistance and ac susceptibility is almost
insensitive to the content of 2212 phase, the qualitative behavior of the Hall
resistance is strongly influenced by the presence of both phases. Theoretical
calculation of Hall resistance has been made based on effective medium
approximation and compared with experimental results.Comment: 7 pages, 7 figure
Transverse voltage in zero external magnetic fields, its scaling and violation of the time reversal symmetry in MgB2
The longitudinal and transverse voltages (resistances) have been measured for
MgB in zero external magnetic fields. Samples were prepared in the form of
thin film and patterned into the usual Hall bar shape. In close vicinity of the
critical temperature T non-zero transverse resistance has been observed.
Its dependence on the transport current has been also studied. New scaling
between transverse and longitudinal resistivities has been observed in the form
. Several models for explanation of the
observed transverse resistances and breaking of reciprocity theorem are
discussed. One of the most promising explanation is based on the idea of
time-reversal symmetry violation
Scaling of resistivities and guided vortex motion in MgB2 thin films
Longitudinal and transverse voltages have been measured on thin films of MgB2
with different superconducting transition widths. The study has been performed
in zero and non-zero external magnetic fields. The non-zero transverse voltage
has been observed in close vicinity of the critical temperature in zero
external magnetic field, while further away from Tc this voltage becomes zero.
In magnetic field it becomes a transverse voltage which is an even function
with respect to the direction of the field. The usual Hall voltage starts to
appear with increasing magnetic field and in large fields the even voltage
disappears and only the Hall voltage is measurable (i.e. the transverse even
voltage is suppressed with increasing magnetic field and increasing transport
current). New scaling between transverse and longitudinal resistivities has
been observed. This correlation is valid not only in the zero magnetic field
but also in nonzero magnetic field where transverse even voltage is detected.
Several models trying to explain observed results are discussed. The most
promising one seems to be guided motion of the vortices, though further
theoretical work will be required to confirm this
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