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Highly oriented films of BaFe12O19 have been deposited onto MgO (111) substrates by pulsed laser ablation deposition. In contrast to epitaxial BaFe12O19 films grown on Al2O3 (001) substrates, these films experience an in-plane biaxial compressive stress, and do not crack or delaminate to thicknesses of at least 28 μm. X-ray diffraction, magnetometry, torque magnetometry, and ferrimagnetic resonance results all indicate excellent c-axis orientation normal to the film plane, and magnetic properties comparable to bulk values. The thickness and properties of these films approach those required for applications in low-loss self-biased nonreciprocal microwave devices.

Magnetic fringe fields emanating from a multiferroic heterostructure composite of Terfenol-D and lead magnesium niobate-lead titanate were utilized to actively tune a meander line microstrip ferrite phase shifter operating above ferrimagnetic resonance at C-band. Differential phase shifts of 65° were measured when tuned with an applied voltage to the multiferroic heterostructure. This demonstration of magnetoelectric field generation provides an alternative approach to tuning broadband planar microwave magnetic devices where neither strain nor direct electromagnetic coupling is experienced between device and multiferroic transducer.

The tuning of Neel temperature by greater than 100 K in nanoparticle Mn-ferrite was demonstrated by a growth-rate-induced cation inversion. Mn-ferrite nanoparticles, having diameters from 4 to 50 nm, were synthesized via coprecipitation synthesis. The Neel temperature (TN) increased inversely to the cation inversion parameter, δ (i.e., defined as (Mn1−δFeδ)tet[MnδFe2−δ]octO4). Concomitantly, TN increased with increased particle growth rate and particle size. These results unambiguously establish cation inversion as the dominant mechanism in modifying the superexchange leading to enhanced TN. The ability to tailor TN enables greater flexibility in applying nanoparticle ferrites in emerging technologies.

Employing a new experimental technique to measure magnetoelectric response functions, we have measured the magnetoelectric effect in composite films of nanogranular metallic iron in anatase titanium dioxide at temperatures below 50K. A magnetoelectric resistance is defined as the ratio of a transverse voltage to bias current as a function of magnetic field. In contrast to the anomalous Hall resistance measured above 50K, the magnetoelectric resistance below 50K is significantly larger and exhibits an even symmetry with respect to magnetic field reversal H→−H. The composite films are unique in terms of showing magnetoelectric effects at low temperatures, 50K.

Hexagonal barium ferrite (BaFe12O19) thin films were grown at the atomic scale by alternating target laser ablation deposition (ATLAD) of orthorhombic BaFe2O4 and rhombohedral α-Fe2O3 on ⟨00l⟩ Al2O3 substrates. Crystallographic, magnetic, and microwave properties of the ATLAD films were determined to be comparable with single crystal quality bulk and films of BaFe12O19 produced by other techniques. The ability to deposit high quality hexagonal ferrite thin films by utilizing multiple targets of different chemical compositions in the deposition routine provides unique opportunities to control the ionic distribution in the unit cell of this important class of ferrite materials.

Programmable defect-free self-assembled magnetic nanowire arrays were produced by using specially designed nano-magnet arrays and external magnetic field. Nickel nanowires were grown on nanoporous template using electrodeposition technique. Magnetic properties, structure and morphology were studied carefully by using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Individual magnetic nanowires were successfully trapped between the nanomagnet pairs with a width of 200 nm and a thickness of 100 nm. Templated self-assembly of magnetic nanowires was successfully demonstrated with Permalloy nano-magnet arrays in both 1D and 2D.

Hexagonal BaFe12O19 ferrite films, having thicknesses ranging from 200–500μm, were prepared by a screen printing process followed by sintering heat treatments. Structural, magnetic, and microwave measurements confirmed that the polycrystalline films were suitable for applications in self-biasing microwave devices in that they exhibited a large remanence (4πMr=3800G), high hysteresis loop squareness (Mr∕Ms=0.96) and low microwave loss. A derivative linewidth ΔH of 310 Oe was measured at 55.6 GHz. This represents the lowest ΔH measured in polycrystalline hexaferrite materials. ΔH can be further improved by reducing porosity and improving the c-axis orientation of grains in polycrystalline ferrite.

The oxygen pressure dependence of magnetic anisotropy in pulse laser deposited manganese ferrite (MnFe2O4) films was investigated. Magnetic anisotropy fields (Ha) are shown to exceed 5kOe when films were processed at oxygen pressures below 5mTorr. Further, it is shown that the magnetically preferred direction of Ha can be aligned either along the film plane (pO2 8mTorr). The ability to induce large perpendicular magnetic anisotropy in spinel ferrites allows for new applications (i.e., phase shifters, filters, isolators, and circulators) near or above X-band frequencies to be considered.