MEASUREMENT OF THE SWITCHING PROPERTIES OF A REGULAR 2-D ARRAY OF PREISACH-TYPE PARTICLES

A two dimensional array of 42 mum square pixels has been etched from a highly uniaxial 3 mum thick magnetooptical garnet film. Each pixel ha s a rectangular hysteresis loop, characterized by ''up'' and ''down'' switching fields H+ and H-, coercivity and interaction fields, H(c) an d H(i). The distribution of H(c) and H(i) has been obtained by measuri ng hysteresis loops of individual pixels using an optical magnetometer . The distributions are found to be Gaussian, with the mean value coer civity H(c) = 258 Oe and a standard deviation of coercivity of sigma(c ) = 85 Oe. The mean interaction field H(i) = 0 Oe with a standard devi ation of sigma(i) = 9 Oe. The effect of the state of the magnetization of the surrounding ''particles'' on a given pixel is characterized by dH(i)/dn = 26 Oe, where n is the number of first neighbors being alre ady switched. The number of up and down magnetized pixels versus magne tic field was counted in a polarizing microscope equipped with a magne tizing coil and thus, the magnetization and the Preisach function can be determined directly, making the identification problem straightforw ard for this simple Preisach system.