This paper presents an up-to-date magnetic material investigation and overview on magnetic materials used in rotating electrical machines. The focus is on small to medium-sized high-performance and high-efficiency permanent-magnet and induction motors for different application scenarios. The investigated materials include silicon-iron, nickel-iron, and cobaltiron lamination steels, as well as soft magnetic composites and amorphous magnetic materials. The technical focus is on the magnetic properties and iron losses as well as the manufacturing influence and required thermal treatments during the manufacturing process. A new loss to flux density factor is introduced to compare the BH magnetization curve and the iron losses of different materials in the same diagram. The aim of the paper is to give the machine designer an efficient material overview and selection guide during the early machine design process. Index Terms-AC machines, amorphous magnetic materials,