Self-consistent theory and simulation of quasiuniform states in thin rectangular magnetic nanoparticles

A self-consistent theory of the ground-state nonuniform magnetization distribution in small magnetic nanoelements is proposed, valid for thicknesses much less than the exchange length, and with natural fulfillment of boundary conditions allowing application to a variety of element shapes. The theory is applied to rectangular 2p(1)l x 2p(2)l x 2l permalloy elements. In contrast to that of square elements, there exists a range of particle sizes having an "intermediate" ground state (mixed flower and leaf symmetries) with average magnetization inclined at phi to the longer edge. With increasing p(1)/p(2) (p(2) fixed), phi gradually decreases to zero (flower state). This intermediate-->flower transition is of the second type, unlike the leaf-->flower transition (first type) observed in square elements with reduction in p(1)(=p(2)). Simulation results support the analytic theory. (C) 2001 American Institute of Physics.