LAUSR

Abstract In this work, conical-shaped M-type ferrite (BaFe12O19, BaM) magnetic nanodot arrays have been prepared on alumina substrate by pulsed laser deposition (PLD) through an ultrathin alumina mask (UTAM). The UTAM has periodically ordered cylindrical holes with a diameter of 350 nm and an interpore distance of 450 nm. Nanodots with a shape distribution in which the diameter is centred at 327 nm with a standard deviation of 23 nm have been fabricated. The microstructures, morphologies and magnetic properties of the nanodot arrays were investigated. Scanning electron microscopy and X-ray diffraction revealed that the prepared nanodots are c-axis-oriented conical crystals. The hysteresis loops indicated that the BaM nanodot arrays have a 63% squareness ratio, which is significantly higher than that of the film (45%). The first-order reversal curve (FORC) diagram showed the nanodots have small distributions of coercivity (Hc) and interactive field (Hu) between particles, with the centre at Hc = 1800 Oe and Hu = −280 Oe. Furthermore, the micromagnetic simulation revealed that this unique structure greatly impacts the distribution of demagnetizing field and effectively reduces the intensity of demagnetizing field.