摘要:

We have measured ac magnetoresistance in fields up to 8 T in a variety of YBa2Cu3O7−&dgr;single crystals containing (a) twin boundaries only in one direction, (b) multi‐twin domain structure, and (c) growth steps. We find two components of the resistance: an angulardependentLorentz force induced ‘‘excess resistivity’’ superimposed on an angularindependentresistivity. The temperature and magnetic field dependence of the angular‐dependent resistivity exhibit a strong correlation with crystal defects, whereas the angular‐independent resistivity remains virtually unchanged. In addition, we find crystals exhibiting both ohmic and non‐ohmic behavior in theirI‐Vcharacteristics depending on crystal imperfections.

ISSN:0003-6951    

DOI:10.1063/1.103458

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The relativistic multiresonator magnetron is analyzed in cylindrical geometry, using the two‐dimensional particle‐in‐cell simulation codemagic. Detailed comparisons are made between the simulation results and the experiments by A. Palevsky and G. Bekefi [Phys. Fluids22, 986 (1979)] using the A6 magnetron configuration. Within a constant scale factor, the computer simulations show a similar dependence of microwave power on magnetic field, with dominant excitations in the &pgr; and 2&pgr; modes. In the preoscillation regime, the electron flow in the simulations differs substantially from the ideal Brillouin flow model. In the nonlinear regime, the saturation is dominated by the formation of spokes.

ISSN:0003-6951    

DOI:10.1063/1.103459

出版商:AIP    

年代:1990

数据来源: AIP