Micromagnetics of thermally activated switching in nonuniformly magnetizednanodots

Patterned magnetic elements are being proposed as media for the future ultr ahigh density storage systems. The equilibrium states of different patterne d magnetic dots at zero temperature have been studied in numerous micromagn etic works,while in the last year some studies have begun to include the ef fect of temperature in the computations. In this research a stochastic dyna mic micromagnetic study is carried out for rectangular magnetic dots with s ize 10 by 3.1 times the exchange length, patterned in a film with a thickne ss of 5 times the exchange length. Two kinds of nonuniform magnetized nanod ots are studied in detail: those in which the state prior to the switching follows the shape of a 'C' and those following an 'S'. In both cases a fiel d near to the zero-temperature switching field is applied and then the ther mally activated switching is observed. The dependence of the switching time on temperature is analyzed. It is observed how for the 'C' configuration a n Arrhenius-like behavior is obtained in a large temperature window while t his is not the case for the 'S' configuration. The micromagnetic structure of the switching thermally activated modes leading to these behaviors is al so studied. (C) 2001 Elsevier Science B.V. All rights reserved.