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Metamaterials Based on Magnetic Shape Anisotropy for K-band Microwave Applications




OBJECTIVE: Develop a metamaterial utilizing magnetic shape anisotropy of ferromagnetic nanoparticles for operation of ultracompact antenna in the K frequency band of the microwave spectrum.


DESCRIPTION: Metamaterials demonstrating resonant response to electromagnetic radiation in the microwave Ku (12 GHz to 18 GHz) and K (18 GHz to 26.5 GHz) bands are highly desirable for multiple applications, including ultracompact microwave antennae, radar detection and frequency-selective wireless heating. Availability of ferromagnetic materials with high saturation magnetization and low magnetic damping [1,2], combined with recent advances in nanolithography, enable the development of such metamaterials based on arrays of ferromagnetic nanoparticles, where the resonance frequency of the metamaterial is determined by the magnetic shape anisotropy of the nanoparticles [3]. The shape anisotropy enables fabrication of devices with a selection of operation frequencies via lithography. For example, arrays of ultracompact antennae covering a wide band of the microwave spectrum, where each antenna is tuned to its own resonance frequency via control of the fabricated nanoparticle shape, can be used for ultrafast monitoring of the electromagnetic environment. An important advantage of a magnetic metamaterial is independence of its resonance frequency on the antennae dimensions [4], which enables ultracompact antennae for communications with miniature devices. The metamaterial antenna gain can be further boosted via magneto-electric or magneto-resistive effects in nanoparticle-based heterostructures to reach record levels of sensitivity to microwave signals [5].


The goal of this proposal is development of magnetic metamaterials based on arrays of ferromagnetic nanoparticles that show resonant response to electromagnetic radiation tunable by the nanoparticle shape. The metamaterial must operate at room temperature without a bias magnetic field and must show tunability of its frequency via shape anisotropy in the 2 GHz – 26.5 GHz frequency range (covering S, C, X, Ku and K bands). The metamaterial must exhibit resonant response to the frequency of incident electromagnetic radiation with the quality factor exceeding 100. To enable commercial applications, the metamaterial must be fabricated from a polycrystalline or amorphous ferromagnetic film deposited at room temperature by a high-throughput technique such as sputtering or electrodeposition. Operation of a K-band ultra-compact microwave antenna based on the shape-anisotropy metamaterial must be demonstrated. The overall antenna dimensions must not exceed 5 millimeters.


PHASE I: Develop a magnetic metamaterial defined by arrays of ferromagnetic nanoparticles that shows resonant response to electromagnetic radiation in the microwave Ku band (12 GHz – 18 GHz) at zero magnetic field and scalability of the concept to the K frequency band.


PHASE II: Determine the optimal combination of high saturation magnetization and low magnetic damping to demonstrate resonant response of the metamaterial in the K frequency band (18 GHz to 26.5 GHz) with the resonance quality factor exceeding 100 throughout that frequency band. The metamaterial fabrication process must be compatible with standard high-throughput film deposition. Demonstrate control of the resonance frequency by shape anisotropy and fabricate metamaterial samples operating in the S, C, X and Ku microwave bands. Design, implement and test an ultra-compact (dimension below 5 mm) K-band antenna based on the shape-anisotropy metamaterial. Demonstrate the possibility of higher antenna gain using magneto-electric or magneto-resistive effects. Provide a sample of the metamaterial and the K-band antenna to the Army for further testing.


PHASE III DUAL USE APPLICATIONS: The ultracompact microwave antennae based on shape-anisotropy magnetic metamaterial can be used as receivers in miniature autonomous vehicles. An array of such ultracompact microwave antennae enables continuous monitoring of the electromagnetic spectrum over a wide microwave band, which can be used for rapid detection of threats with known electromagnetic signatures.



  1. M. A. W. Schoen, D. Thonig, M. L. Schneider, T. J. Silva, H. T. Nembach, O. Eriksson, O. Karis, J. M. Shaw, Ultra-low magnetic damping of a metallic ferromagnet. Nat. Phys. 12, 839–842 (2016).;
  2. N. Ji, X. Liu, J.-P. Wang, Theory of Giant Saturation Magnetization in α-Fe16N: Role of Partial Localization in Ferromagnetism of 3d Transition Metals, New J. Phys. 12, 063032 (2010).;
  3. C. Bayer, J. Jorzick, B. Hillebrands, S. O. Demokritov, R. Kouba, R. Bozinoski, A. N. Slavin, K. Y. Guslienko, D. V. Berkov, N. L. Gorn, M. P. Kostylev, Spin-Wave Excitations in Finite Rectangular Elements of Ni80Fe20, Phys. Rev. B 72, 064427 (2005).;
  4. Y. Malallah, K. Alhassoon, D. Venkatesh, A. S. Daryoush, C. Chinnasamy, M. Marinescu, and H. Gundel, Gain Improved Stacked Antenna Tuned Using Ferromagnetic Nanoparticles and Ferroelectrics Films, in 2016 46th European Microwave Conference (EuMC) (2016), pp. 1007–1010.;
  5. B. Fang, M. Carpentieri, X. Hao, H. Jiang, J. A. Katine, I. N. Krivorotov, B. Ocker, J. Langer, K. L. Wang, B. Zhang, B. Azzerboni, P. Khalili Amiri, G. Finocchio, Z. Zeng, Giant Spin-Torque Diode Sensitivity in the Absence of Bias Magnetic Field, Nature Commun. 7, 11259 (2016).


KEYWORDS: magnetic metamaterial, shape anisotropy, microwave antenna, nanolithography, magnetic resonance

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