The present invention concerns a powder magnetic core for operating at high frequencies obtained by pressure forming an iron-based magnetic powder covered with an insulation film, and a specific resistance less than 1000, preferably less than 2000 and most preferably less than 3000 µm, a saturation magnetic flux density B above 1.5, preferably above 1.7 and most preferably above 1.9 (T). The invention also concerns the preparation of such cores as well as a powder which is suitable for the preparation.