Univ Santiago Chile Dept Fis Casilla 307 Santiago 2 Chile
Max Planck Inst Festkorperforsch D-70569 Stuttgart Germany
Univ La Frontera Dept Fis Temuco Chile

We investigate the hysteresis curve of a 2D Random Bond Ising Model (RBIM) with anti- (AF) and ferromagnetic (F) couplings at concentration of 50\% each. The hysteresis curves show magnetization jumps (first order transitions) at well defined magnetic fields indicating topological blocking effects caused by frustration domains in the system.
 

Revista Mexicana de Fisica, 44 78-80, 1998.