MAJOR LOOP RECONSTRUCTION FROM SWITCHING OF INDIVIDUAL PARTICLES

Major hysteresis loops of groups of isolated 60 mu m square garnet par ticles of a regular two-dimensional array, have been measured magnetoo ptically. Individual loops for each particle were measured, and the st atistics of the distribution of coercivities and interaction fields wa s determined. It is shown that from the measured coercivity distributi on and calculated magnetostatic interaction fields the major hysteresi s loop can be reconstructed. The switching sequence, and the major loo p of an assembly of 5x5 particles were calculated numerically for two cases: first, when calculating the magnetostatic interaction, the 25 p articles were assumed to be isolated; second, the major loop of the sa me 25 particles, embedded into a 9X9 square, was reconstructed taking into account the interactions among all 81 particles. The numerically simulated major hysteresis loops agree very well with the measured loo ps, demonstrating the reliability of numerical modeling. (C) 1997 Amer ican Institute of Physics.