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Aerosol deposition is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95 pct of the theoretical value. The primary advantage of aerosol deposition is that the deposition takes place entirely at room temperature, thereby enabling film growth in material systems with disparate melting temperatures. We show representative characterization results of yttrium iron garnet thick films deposited onto a 〈111〉 gadolinium gallium garnet substrate by aerosol deposition using scanning electron microscopy, X-ray diffraction, profilometry, vibrating sample magnetometry, and ferromagnetic resonance. To further elucidate the effect of density and grain size on the magnetic properties, we perform post-deposition annealing of the films to study the effect on the structural and magnetic properties of the films. Our results indicate that our system can successfully deposit dense, thick yttrium iron garnet films and that with moderate annealing the films can achieve a ferromagnetic resonance linewidth comparable to that reported for polycrystalline films deposited by other higher temperature growth techniques.

We report room-temperature negative magnetoresistance in ferromagnet–graphene–ferromagnet (FM|Gr|FM) junctions with minority spin polarization exceeding 80%, consistent with predictions of strong minority spin filtering. We fabricated arrays of such junctions viachemical vapor deposition of multilayer graphene on lattice-matched single-crystal NiFe(111) films and standard photolithographic patterning and etching techniques. The junctions exhibit metallic transport behavior, low resistance, and the negative magnetoresistance characteristic of a minority spin filter interface throughout the temperature range 10 to 300 K. We develop a device model to incorporate the predicted spin filtering by explicitly treating a metallic minority spin channel with spin current conversion and a tunnel barrier majority spin channel and extract spin polarization of at least 80% in the graphene layer in our structures. The junctions also show antiferromagnetic coupling, consistent with several recent predictions. The methods and findings are relevant to fast-readout low-power magnetic random access memory technology, spin logic devices, and low-power magnetic field sensors.

Epitaxial VO2/TiO2thin film heterostructures were grown on (100) (m-cut) Al2O3substrates via pulsed laser deposition. We have demonstrated the ability to reduce the semiconductor–metal transition (SMT) temperature of VO2to ∼44 °C while retaining a 4 order of magnitude SMT using the TiO2buffer layer. A combination of electrical transport and X-ray diffraction reciprocal space mapping studies help examine the specific strain states of VO2/TiO2/Al2O3heterostructures as a function of TiO2film growth temperatures. Atomic force microscopy and transmission electron microscopy analyses show that the columnar microstructure present in TiO2buffer films is responsible for the partially strained VO2film behavior and subsequently favorable transport characteristics with a lower SMT temperature. Such findings are of crucial importance for both the technological implementation of the VO2system, where reduction of its SMT temperature is widely sought, as well as the broader complex oxide community, where greater understanding of the evolution of microstructure, strain, and functional properties is a high priority.

We have employed the aerosol deposition method (ADM) to direct-write 39-µm-thick polycrystalline films of yttrium iron garnet at room temperature onto sapphire at a rate of 1-3 µm/min as a first step toward integration into microwave magnetic circuits. The resulting randomly oriented polycrystalline films are composed of fractured compact nanosized crystallites. Upon postdeposition sintering at 1280 °C the density and magnetic properties become closer to those of the bulk. These results suggest that the ADM shows promise for depositing very thick films at high deposition rates to produce structurally and magnetically uniform films that retain the structural properties of the starting powder.