[en] Magnetic field-structured composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g., rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chainlike particle structures, and a biaxial field produces sheetlike particle structures. 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 decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCs of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material. (c) 2000 The American Physical Society

[en] The soft magnetic properties of the nanocrystalline Fe endash M endash B (M=Zr,Nb) alloys, which exhibit a high saturation flux density (B_s) above 1.5 T as well as a high effective permeability (μ_e) above 30000 at 1 kHz, were found to be improved by adding small amounts of Cu and by optimizing the chemical composition. The addition of Cu to the alloys decreases the bcc grain size. The excellent soft magnetic properties (a high μ_e of 100000 at 1 kHz combined with a high B_s of 1.53 T) can be achieved in the region where small grain size, as well as nearly zero-magnetostriction are obtained, which is attained in the compositional range around Fe₈₄Nb_3.5Zr_3.5B₈Cu₁. The soft magnetic properties can be further improved by low temperature annealing before the crystallization treatment, probably as a result of a decreased grain size distribution in the crystallized state. Consequently, the μ_e reaches the maximum value of 120000 for the nanocrystalline Fe₈₄Nb_3.5Zr_3.5B₈Cu₁ alloy. copyright 1997 American Institute of Physics

[en] The magnetic stability of two different interfacial exchange coupled systems is investigated using the magneto-optic Kerr effect during repeated reversal of the soft layer magnetization by field cycling up to 10⁷ times. For uniaxial Fe/Cr(211) exchange biased ''double-superlattice'' systems, small but rapid initial decay of exchange bias field H_E and the remanent magnetization is observed. Also the Sm-Co/Fe bilayers grown epitaxially with uniaxial in-plane anisotropy show similar decay. However, the H_E of biaxial and random in-plane bilayers shows gradual decay without large reduction of the magnetization. These different decay behaviors are explained by their different microstructure and interfacial spin configurations. (c) 2000 American Vacuum Society