Distinguishing local moment versus itinerant ferromagnets: Dynamic magnetic susceptibility

Radio-frequency measurements of dynamic magnetic susceptibility of various ferromagnets show striking differences between local-moment ferromagnetism (LFM) and weak itinerant ferromagnetism (IFM) ferromagnetic systems. LFMs show a very sharp peak in susceptibility in the vicinity of the Curie temperature T(C) that rapidly decreases in amplitude and shifts to higher temperature with the application of a weak dc bias field. In stark contrast, the generally accepted IFM systems show no peak, but rather a broad maximum well below T(C). The temperature of this maximum shifts to lower values and the amplitude is suppressed with an applied dc field. (c) 2008 American Institute of Physics.