Magnetic microwires as macrospins in a long-range dipole-dipole interaction

The long-range dipole-dipole interaction in an array of ferromagnetic micro wires is studied through magnetic hysteresis measurements and Monte Carlo s imulation. The experimental study has been performed on glass-coated amorph ous Fe77.5Si7.5B15 microwire with diameter of 5 mu m and lengths from 5 to 60 mm. Hysteresis loops performed at room temperature for an array of N mic rowires (N = 2, 3, 3, and 5) exhibit jumps and plateaux on the demagnetizat ion, each step correspondent to the magnetization reversal of an individual wire. A model has been constructed taking into account the fact that the m agnetization reversal is nucleated at the ends of each wire, under the infl uence of a dipolar field due to all other wires. Measurements for two wires allowed us to conclude that the dipolar field (or constant coupling) is in dependent of distance, at least for an array of a few wires. With the excep tion of three wires, where frustration seems to be present, the predicted r eversal fields of our model are in good agreement with measurements. Ln ord er to study the role played by the number of wires on the demagnetization p rocess, we calculate hysteresis loops for a large number of wires through t he Monte Carlo method.