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Epitaxial CoFe2O4 (CFO) films with different thicknesses (6–240 nm) were fabricated on (001) SrTiO3 substrates by reactive cosputtering. Microstructure analyses indicate that the surfaces of the CFO films are covered by islands with height from 2.7 to 0.8 nm upon decreasing film thickness from 240 to 6 nm. Magnetic measurement shows that the CFO films exhibit film thickness dependence of anomalous magnetic properties, including two different “magnetic phases” reflected in the magnetization loops, and reduced saturation magnetization and coercivity with decreasing film thickness. Systematic analyses of the microstructure and magnetization loops for the CFO films with different thicknesses imply that the structure defects on the surface and at the interface, together with the antiphase boundaries in the films are responsible for the anomalous magnetic properties of the CFO films.

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We propose a subwavelength B-shaped metallic hole array filter with an embedded thermally tunable InSb semiconductor bar in the terahertz regime. The resonance frequency of this filter can be actively tuned by controlling the temperature of InSb. The transmissions of the filter are calculated with the finite-difference time domain method at various temperatures. Narrowband THz wave with the full width at half maximum of 235 GHz can be selected in the frequency range from 0.74 to 2.02 THz at temperatures from 160 to 350 K.