A powder magnetic core is provided for operating at high frequencies that is obtained by pressure forming an iron-based magnetic powder covered with an insulation film, which has a specific resistance more than 1000, preferably more than 2000, and most preferably more than 3000 μΩm, and a saturation magnetic flux density B above 1.5, preferably above 1.7, and most preferably above 1.9 (T). A method for the preparation of such cores as well as a powder which is suitable for the preparation also are provided.