Static and dynamic magnetic properties of fine CoNi and FeCoNi particles synthesized by the polyol process

Fine CoNi and FeCoNi particles elaborated by the polyol process over a wide size range display a core shell texture. From the study of the coercivity and remanence against the particle size, the critical size below which the CoNi particles are single domains is estimated in the 20-40 nm range. The c omparison between static and dynamic properties shows that exchange resonan ce modes are observed for non single domain particles. Anisotropy constants are found to increase as the particle size decreases and as the Co content increases.