<p>This thesis compiles results of research in two mutuallydependent parts: 1) development of ferromagnetic resonance(FMR) spectrometer to study microwave properties offerromagnetic materials, and 2) characterization of new irongarnets: pulsed laser deposited Y<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>and Bi<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>films and Ce:Y<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>single crystal.</p><p>First part describes a novel<i>Broadband</i>FMR<i>Spectrometer</i>designed to characterize thin ferromagneticfilms. The spectrometer uses two probeheads: one is the X-bandmicrowave reflection cavity for room temperature measurementsand the in-cryostat microstrip line probe to perform FMRexperiments in the frequency range from 50 MHz to 40 GHz. Veryuniform and stable magnetic field up to 2.4 T, temperatures 4 Kto 420 K, and continuous frequency scan performed by<i>HP8722D</i>vector network analyzer provide various modes ofoperation. Both probeheads are equipped with two-circlegoniometers to ensure accurate study of magneticanisotropy.</p><p>The spectrometer was used to make express-analysis ofquality thus to optimize processing parameters of epitaxialiron garnet films grown by pulsed laser deposition (PLD).Comprehensive study of uniaxial and cubic magnetocrystallineanisotropy has been performed for Ce:Y<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>bulk crystal as well as for Y<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>and Bi<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>films grown on different substrates by PLD andreactive ion beam sputtering techniques. BroadbandFMR-spectroscopy revealed difference in spectra of domain wallresonances: instead ofsoftspin modes in filmsgrown by liquid phase epitaxy, PLD-made films showdiffusetransformation of domains near thesaturation field. This effect indicates non-uniformity ofsaturation magnetization and field of uniaxial anisotropy inPLD-iron garnets. Spin wave resonances in comparison withuniform FMR have been studied to evaluatelocalqualityof ferromagnetic films. The resonance field andFMR linewidth behavior were studied at various crystallographicdirections determined by X-ray diffraction.</p><p>FMR was used to choose PLD-made YIG films with low losses atmicrowave frequencies and to build magnetostatic surface wavesmicrowave bandpass filter. The filter was designed as a planarfilm structure with a microstrip line for transducers. It is afirst demonstration of feasibility to introduce PLD processingtechnique to magnetostatic wave technology.</p><p>Magneto-optical study of Ce:Y<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>single crystal complements results ofFMR-spectroscopy of new garnets.</p><p><b>Keywords:</b>ferrites, thin films, ferromagnetic resonance,microwaves, FMR spectrometer, magnetic anisotropy,magnetostatic waves.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:kth-3602 |
| Date | January 2003 |
| Creators | Denysenkov, Vasyl |
| Publisher | KTH, Microelectronics and Information Technology, IMIT, Kista : Mikroelektronik och informationsteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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