Nanomagnetics with lasers

Both liquid and vapour phase pulsed laser deposition (PLD) techniques have been used to synthesize nanophase magnetic alloys of CoPt. While the liquid route results in soft phase (disordered fcc) nanoparticles of CoPt near equiatomic composition dispersed in a surfactant-polymer matrix, the conventional vapour phase PLD allows growth of high coercivity nanoscale structures of CoPt on (001) SrTiO3. The magnetization, M(T), dynamics of the colloidal particles is examined. Two distinct particle distributions are established from analysis of M(T) data, in conformity with results of electron microscopy. In vapour deposited films at low growth rate (∼0.4 A/s), morphology changes from a self-similar fractal to nanodots as the deposition temperature is raised from 700–800°C. The large lattice mismatch between (001) SrTiO3 and the ac/bc plane of L10 ordered phase imparts tensile strain to the films whose morphological manifestations can be suppressed at high growth rates.