Size effects of switching fields of thin Permalloy particles

Measurements of hysteresis loops were performed on thin Permalloy rectangular platelets with various dimensions prepared by nanolithography. The particle coercivity H_c exhibits a sensitive size dependence. The measured values of H_c are compared with micromagnetic predictions utilizing two-dimensional models without magnetization variation through the thickness. Excellent overall agreement is found, indicating that a simplified two-dimensional approach is sufficient for characterizing reversal mechanisms for particles with thicknesses smaller than or comparable to the exchange length