@article{rasic_vlahovic_schwartz_2016, title={Underlying causes of the magnetic behavior in surface patterned NiFe2O4 thin films}, volume={6}, ISSN={["2159-6867"]}, DOI={10.1557/mrc.2016.38}, abstractNote={Surface patterned NiFe_2O_4 thin films exhibited large reduction in coercivity as compared with the films without surface patterning. Chemical analysis of the films revealed that there was no diffusion between the film and the substrate. Additional heating was shown to improve saturation magnetization without adverse effect on coercivity. The process of imprinting was eliminated as the possible cause of the phenomena as the flat stamp did not alter the magnetic properties of the film. Finally, it was shown that the orientation of the features with respect to the magnetic field does not have a significant effect on the magnetic response.}, number={4}, journal={MRS COMMUNICATIONS}, author={Rasic, Goran and Vlahovic, Branislav and Schwartz, Justin}, year={2016}, month={Dec}, pages={397–401} }
 @article{rasic_schwartz_2015, title={On the origin of coercivity reduction in surface patterned magnetic thin films}, volume={212}, ISSN={["1862-6319"]}, DOI={10.1002/pssa.201431434}, abstractNote={Spinel nickel ferrite (NiFe2O4) is a promising material for next generation high‐frequency sensors, antennae and microwave devices. A key issue to be addressed is the magnetic loss, which is proportional to frequency and becomes substantial at frequencies above 1 GHz. Previously, we reported on coercivity reduction in NiFe2O4 through surface patterning (Rasic and Schwartz, MRS Commun. 3, 207 (2013) and IEEE Magn. Lett. 5, 1 (2014) ). Here, we report on the effects of varying the feature size on magnetic behavior, including loss, and explain the reduced coercivity theoretically. Nickel ferrite thin films were deposited on c‐plane sapphire substrates using chemical solution deposition and patterned via nanoimprint lithography with patterning masters having feature sizes varying from 500 to 1500 nm in 200 nm increments. Atomic force microscopy showed good feature transfer for all samples. X‐ray diffraction images showed all samples to be single‐phase inverse spinel nickel ferrite with similar texture. All patterned samples showed coercivity reductions relative to the unpatterned samples. The effects of feature size on coercivity reduction showed opposite trends for in‐plane and out‐of‐plane magnetization hysteresis measurements, whereas saturation magnetization was not affected by feature size changes. Magnetic force microscopy images confirmed the origin of coercivity reduction to be shape‐anisotropy‐forced alternating domain formation. The coercivity reduction phenomena observed in patterned NiFe2O4 thin films are explained theoretically. The effect of changing the film thickness and domain size on the equilibrium energy density was calculated. While the relative energy density showed a stable equilibrium, the energy increase for domain sizes equaling that of patterned films in this study was small. Finally, the new domain structure in patterned NiFe2O4 films was explained within micromagnetism theory.}, number={2}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Rasic, Goran and Schwartz, Justin}, year={2015}, month={Feb}, pages={449–458} }
 @article{rasic_schwartz_2014, title={Coercivity reduction in nickel ferrite (NiFe2O4) thin films through surface patterning}, volume={5}, journal={IEEE Magnetics Letters}, author={Rasic, G. and Schwartz, J.}, year={2014} }
 @article{rasic_schwartz_2013, title={Nanoimprint lithographic surface patterning of sol-gel fabricated nickel ferrite (NiFe2O4)}, volume={3}, DOI={10.1557/mrc.2013.44}, abstractNote={Textured nickel ferrite (NFO, NiFe_2O_4) thin films were deposited at room temperature by chemical solution deposition onto c -plane sapphire substrates. A nanoimprint lithography technique using a polydimethylsiloxane stamp was used to transfer a pattern from a master to the thin film, which was subsequently annealed to crystallize the NFO. Atomic force microscopy scans showed good periodicity and feature profile over a large area which was confirmed with cross-sectional transmission electron microscopy. X-ray diffraction revealed textured single-phase inverse spinel NFO. Magnetic measurements of patterned thin films showed a large reduction in coercivity due to demagnetization factors.}, number={4}, journal={MRS Communications}, author={Rasic, G. and Schwartz, J.}, year={2013}, pages={207–211} }
 @article{seifikar_calandro_rasic_deeb_yang_bassiri-gharb_schwartz_2013, title={Optimized Growth of Heteroepitaxial (111) NiFe2O4 Thin Films on (0001) Sapphire with Two In-Plane Variants via Chemical Solution Deposition}, volume={96}, ISSN={["1551-2916"]}, DOI={10.1111/jace.12520}, abstractNote={(111)‐oriented epitaxial thin films of nickel ferrite (NFO) are grown on c‐plane sapphire [α‐Al2O3(0001)] substrates using a chemical solution deposition technique. The processing conditions, including pyrolysis and annealing temperatures, are varied to achieve a film that shows maximum texture and epitaxy. It is shown that increasing the pyrolysis temperature to 400°C and decreasing the annealing temperature to 750°C for 10 min result in the highest degree of texture in the films. Lower film thickness also leads to a higher degree of texture. Microstructural studies confirm an in‐plane epitaxial relationship between the (111) NFO film and the (0001) Al2O3 substrate in two variants, [110]NFO ||  or .}, number={10}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Seifikar, Safoura and Calandro, Bridget and Rasic, Goran and Deeb, Elisabeth and Yang, Jijin and Bassiri-Gharb, Nazanin and Schwartz, Justin}, year={2013}, month={Oct}, pages={3050–3053} }