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Highly zero-biased magnetoelectric response in magnetostrictive/piezoelectric composite J. Appl. Phys. 112, 024504 (2012) Resonance magnetoelectric effects in a layered composite under magnetic and electrical excitations J. Appl. Phys. 112, 014103 (2012) Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillarsThe magnetic structure of small CoFe Z 0 4 particles has been investigated as a function of the particle size. Samples (in the 10-100 nm size range and up) were prepared by chemical precipitation followed by a heat treatment at relatively low temperatures. M6ssbauer spectra of the 57Fe nuclei, obtained with a longitudinal magnetic applied field, unambiguously establish that a noncollinear structure exists that is most pronounced for the smallest particles. The analysis indicates that a surface effect of the crystallites that make up a particle is the origin of this phenomenon. A model is proposed in which the CoFe 2 0 4 crystallites that make up a particle consist of a core with the usual spin arrangement and a boundary surface layer with atomic moments inclined to the direction of the net magnetization. The temperature dependency of this structure is also examined.

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The magnetic structure of small NiFe2O4 particles has been investigated. Samples (in the few hundred angstrom size range and up) were prepared by chemical precipitation followed by a heat treatment at relatively low temperatures. Mössbauer spectra of the 57Fe nuclei, obtained with a longitudinal magnetic field applied, unambiguously establish that a non-collinear structure exists. Further, the magnetic moment at low temperatures is appreciably lower than the value reported for bulk material. A model is proposed in which the NiFe2O4 particles consist of a core with the usual spin arrangement and a surface layer with atomic moments inclined to the direction of the net magnetization. The temperature dependence of this structure is also reported.

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Particles of BaFe,,O,,, were prepared by chemical coprecipitation; their magnetic properties were studied. A coercive force of 6000 Oe, one of the highest reported for isotropic BaFe,,O,,, was obtained. X-ray and Moessbauer studies were conducted to examine the mechanism of formation. Superparamagnetic Lu-Fe,O,, was present during synthesis. Ferrites were sintered from these precipitated powders by both the usual method and a hot-press-forging method. The observed magnetic characteristics result from partial orientation of defect-free single-domain coprecipitated powders.