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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 comparison between static and dynamic properties shows that exchange resonance 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. Index Terms---Anisotropy constant, exchange resonance modes, fine ferromagnetic particles, polyol process.