The design of sensor heads for fiber optic interferometric magnetometers is critical when sub‐nano‐Tesla fields are to be measured. Magnetically soft metallic glasses can exhibit large magnetostrictions and are candidates as materials for this application. However, their usefulness is limited at high frequencies through eddy current losses in bulk materials. This paper discusses the use of particulate metallic glasses in an inert binder. Measurements are presented on magnetization and magnetostriction of these composite materials in the quasi‐dc regime. Their dynamic behavior when used as magnetic field sensors is also described.