Magnetics of nonlaminated, bilaminated, and multilaminated permalloy stripes

Abstract

Using the magnetoresistive response technique and the micro-Kerr domain imaging technique, we have studied the magnetics of 2000-Å-thick nonlaminated, bilaminated, and multilaminated permalloy stripes with a length of 2400 μm, widths varying from 100 to 2 μm, and with the uniaxial anisotropy easy axis transverse to the length of the stripes. Results show that stripes from all three types of films exhibit non-single-domain remanent states that are hysteretic in their longitudinal magnetic responses. For the nonlaminated structures, closure domains are formed for the minimization of transverse demagnetization energy. For the laminated structures, longitudinally magnetized regions along the edges are formed as a basic feature of the flux-closure configuration in the laminated films. Furthermore, for the multilaminated structures, the large number of degrees of freedom and the low wall energies have created an abundance of low-energy remanent states that might cause the small-field response of the structure to creep with time. Finally, the use of transverse biasing is found to be ineffective in eliminating hysteresis in the bilaminated structures because this hysteresis is not a consequence of transverse symmetry in the structure.