Anisotropic magnetism in field-structured composites

Magnetic field-structured composites (FSCs) are made by structuring magneti c particle suspensions in uniaxial or biaxial (e.g., rotating) magnetic fie lds, while polymerizing the suspending resin. A uniaxial held produces chai nlike particle structures, and a biaxial held produces sheetlike particle s tructures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decrea sed slightly orthogonal to the structuring field, relative to the unstructu red particle composite. The coercivity is essentially unaffected by structu ring. We present data for FSCs of magnetically soft particles, and demonstr ate that the altered magnetism can be accounted for by considering the larg e local fields that occur in FSCs. FSCs of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the l ocal held effects in combination with the large crystalline anisotropy of t his material.