Abstract
Switching field reduction and applied field dependence of the switching field of 2 to 4-layer exchange coupled composite (ECC) dots were studied. The analysis was performed based on a simple spin-model. For 2-layer ECC dots, minimum switching field normalized by the averaged anisotropy field, h*, was obtained for zero anisotropy for the soft layer. For 3-layer ECC dots, smaller values of h* were obtained for a small anisotropy field, Hk, of the second layer, and minimum h* of 0.46 was obtained. Smallest applied field angle dependence of the switching field was also obtained for the structure with the smallest h*. For 4-layer ECC dots, smaller h* values were obtained for a small Hk of the third layer regardless of Hk of the second layer. The smallest h* value of 0.42 was obtained which is smaller by only 7 % from that for 3-layer ECC dots. It was concluded that 3-layer ECC dots with a small Hk (around 0.2 times of the hard layer) for the second layer is the best choice for practical applications.
