A materials system of ternary full Heusler alloys exhibiting substantial current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) has been theoretically proposed and experimentally realized. Observed trends in magnetoresistance are broadly consistent with the modeling results. A CPP-GMR of 6.7% and ΔRA of 4 mΩ μm2 have been demonstrated in the bottom spin-valve configuration. The spin-stand testing of narrow-track recording heads confirmed compatibility of these materials with hard disk drive reader technology.

Micromagnetic structures in submicron size circular permalloy elements of various thickness (5–50 nm) have been experimentally studied using a magnetic force microscope (MFM). One and two vortex micromagnetic states were observed in the elements. It was found that one vortex state is more favorable under external field of low values, while two vortex state forms under high fields. Switching between one and two vortex states results in a hysteresis in the micromagnetic response of the elements. The transition field from one to two vortex state increases with the increase of element thickness and, therefore, with the increase of the demagnetizing effect of the element edges. The two vortex state was not observed in the elements with a thickness of 50 nm or greater. The micromagnetic behavior correlates with hysteresis loops of a free layer in a magnetic tunnel junction of size, shape, and free layer thickness similar to elements examined with the MFM.

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Perpendicular magnetic anisotropy energy in rf magnetron sputtered amorphous TbFe films is measured to increase exponentially with pair-order anisotropy induced by the selective resputtering of surface adatoms during film growth.

Narrow-track current-perpendicular-to-the-plane giant magnetoresistive heads containing Heusler alloy layer have been fabricated utilizing an abutted junction hard bias design. The head performance has been tested quasistatically and dynamically under high density recording conditions using a perpendicular magnetic recording media.

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Magnetic domain structures on single-crystalline magnetite (Fe3O4) particles, prepared by microfabrication techniques from molecular-beam epitaxial (110) magnetite films grown on MgO, were studied by magnetic force microscopy. The (110) magnetite film thickness was 250 nm and the patterned particles ranged in size from 2×2 to 10×10 μm. The patterned particles showed in-plane, stripe-like domain structures with ill-defined and fragmented walls mainly aligned along the in-plane [110] direction. In both the parent film and the patterned particles, an out-of-plane component of the stray field was observed within domain interiors as a fine-scale (100–300 nm) and spatially variable magnetic contrast present in both the remanent state and in applied fields. Individual wall sections were observed to be highly fragmented with variable widths (100–300 nm) and offsets and subdivided into opposite polarity segments of variable lengths. Remagnetization of a 10×10 μm particle in fields up to 500 Oe occurred by reverse spike domain nucleation at the edge of the particle followed by growth and propagation towards the interior of the particle similar to classical behavior of uniaxial materials. In contrast, the unusual domain wall structures are a consequence of the antiferromagnetically coupled, growth-induced, structural antiphase domains and antiphase boundaries (APB) know to form in epitaxial thin films of magnetite. Magnetically, the particles behave differently at the different length scales. A particle as a whole (micrometer length scale) behaves as a magnetically uniaxial object, but on a smaller length scale (submicron scale), the magnetic microstructure is strongly influenced by the antiphase structural domains. Analysis of the domain spacing as a function of particle size yields an estimate of the average exchange stiffness constant that is nearly 2 orders of magnitude lower than the value in bulk magnetite. This is consistent with the idea that exchange interactions across the APBs are severely suppressed due to spin frustration.