Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

Influence of commensurability effects on the resistive state of Mo/Si and W/Si multilayers in tilted magnetic fields. Lock-in effect and combine vortex lattice

O.I.Yuzephovich, S.V.Bengus, M.Yu.Mikhailov

Institute for Low Temperature Physics and Engineering, Kharkov, Ukraine

Commensurability effects are discovered on Mo/Si and W/Si multilayers, which occurs in parallel to the layers and slightly inclined magnetic fields [1, 2]. At some temperature corresponding to the fitting of the vortex cores within semiconducting interlayers a minimum (or a series of minima) appears on the dependences of the resistivity R on magnetic field  H. At lower temperatures the minimum becomes more pronounced and at last transforms into a large zero resistance region (ZRR). After ZRR in the higher magnetic fields the resistance appears again. This effect may be explained in terms of the intrinsic pinning and vortex lattice (VL) commensurability with underlying layered structure. The locations of the zero resistance regions correspond to the stable VL configurations or to the transitions between two commensurate lattices. The experimental data are in quantitative agreement with the Ivlev, Kopnin, Pokrovsky theory considering VL structure in the case of a strong intrinsic pinning.

The resistive method that based on commensurability effects proposed as a tool of the VL structure study in layered superconductors. This method is applicable to all layered superconducting systems and can be used in strong magnetic fields.

The lock-in transition is observed on Mo/Si [2] which takes place in the weakly tilted magnetic fields. Due to the anisotropy, at relatively small tilting angles the confinement of the vortices parallel to the layer planes becomes energetically more favorable than the creation of tilted vortices. The experimental results are consistent with the theoretical predictions of Feinberg and Villard. In the framework of this visit the lock-in state is firstly observed in W/Si multilayer.

Now we performed investigations of the resistive transitions on the Mo/Si and W/Si multilayers in a wide angle range. It is found that at much larger angles than for lock-in effect in the dependences R(H) reappear pronounced minimum resistance. The magnetic fields corresponding to these minima are shifted with temperature changes. The appearance of these anomalies in the strongly inclined fields can be explained by the combined vortex lattice, predicted theoretically in a number of studies for layered superconductors. Further studies are needed.

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