Thermal stability and switching field distribution of CoNi/Pt patterned media

The thermal dependence and distribution of the switching fields of arrays of magnetic Co50Ni50/Pt nanodots has been studied. These dots, with a diameter of 90 nm, are arranged in a hexagonal pattern with a periodicity of 300 nm. Field-dependent magnetic force microscopy was used to measure the switching field distribution of the array, which was found to range from 80 to 192 kA/m, a value which is confirmed by vibrating sample magnetometer measurements. Additionally, the temperature dependence on the collective behaviour of the switching fields of the array has been investigated. The energy barrier at zero field was estimated to have a value in between 1.8×10−19 and 2.1×10−19 J. Combining this value with the effective anisotropy determined by torque measurements, the switching volume can be estimated to lie in between 1.2×103 and 1.4×103 nm3.