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On ferromagnetic thin films and two-dimensional magneto-optic photonic crystals
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents results in two different neighboring areas of research: the magnetic properties of thin ferrite films and the application of the films in two-dimensional photonic crystals.

In the first part, we investigate the accuracy of the customary method for determining the magnetic anisotropy constants of ferrite films by ferromagnetic resonance (FMR) experiment. We have improved the method and introduced an experimental procedure to obtain the anisotropy constants with higher precision. The magnetic anisotropy fields are obtained by using FMR on a (111)-oriented yttrium iron garnet (YIG) film made by pulsed laser deposition. Moreover, we found experimentally that the shapes of FMR spectra of laser deposited epitaxial YIG films strongly depend on the orientation of the magnetic bias field with respect to the crystalline axes of the film. Inhomogeneities of the constants of anisotropy throughout the film could be responsible for the complexity of the FMR spectra. We find the special directions of the applied magnetic field in which the contribution of the magnetocrystalline anisotropy has the smallest effect on the ferromagnetic resonance and therefore on the elements of the permeability tensor.

In the second part, we study the electromagnetic wave propagation in two-dimensional (2D) dielectric and magneto-optic photonic crystals (PCs). We have proposed a 2D PC which is composed of magneto-optic material for the purpose of the enhancement of Faraday rotation in high transmission. It is assumed that the 2D PC contains a bismuth iron garnet (BIG) film either as the PC background medium or as a defect, embedded in the 2D PC. We have examined theoretically and computationally the increase in the Faraday rotation as well as the transmission of a plane-polarized plane wave incident onto these structures in the optical wavelength regime. Several important phenomena, with potential applications, are observed.

Place, publisher, year, edition, pages
Kista: Mikroelektronik och informationsteknik , 2004.
Series
TRITA-MVT, ISSN 0348-4467 ; 2004:6
Keyword [en]
Physics, photonic crystals, physics
Keyword [sv]
Fysik
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-42OAI: oai:DiVA.org:kth-42DiVA: diva2:11190
Public defence
2004-11-12, C1, Electrum, Kista, 13:00
Opponent
Supervisors
Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2016-11-24
List of papers
1. Microwave and magneto-optic properties of pulsed laser deposited bismuth iron garnet films
Open this publication in new window or tab >>Microwave and magneto-optic properties of pulsed laser deposited bismuth iron garnet films
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2001 (English)In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 37, no 4, 2454-2456 p.Article in journal (Refereed) Published
Abstract [en]

 We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown by pulsed laser ablation of a precursor oxide target onto (NdGd)(3)(ScGa)(5)O-12 [NGSGG(111)] and Gd-3 (ScGa)(5)O-12 (GSGG(001)] single crystals. Comprehensive X-ray diffraction analyses reveal the epitaxial quality of the BIG films: they are single phase, exclusively (111) and (001) oriented with less than 0.4 degrees and 0.06 degrees of the full width at half maximum of the rocking curve of main texture Bragg reflection [(111) for NGSGG and (001) for GSGG substrate, respectively]. The films are strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. VSM and ferromagnetic resonance measurements revealed in-plane magnetization in BIG/GSGG(001) film, while the BIG/NGSGG(111) film was found to have perpendicular magnetization. For BIG(001) and (111) films the saturation magnetization 4 piM(s) was found to be 1400 and 1200 Gs; the Faraday rotation at 635 nm was -7.8 and -6.7 deg/mum; the constant of uniaxial magnetic anisotropy was K-u* = -8.70 X 10(4) and +1.16 x 10(4) erg/cm(3); the constant of cubic magnetic anisotropy K-1 = -3.6 x 10(3) and -7.14 x 10(3) erg/cm(3). High Faraday rotation and low coercive field (less than or equal to 40 Oe) of BIG/GSGG(001) films show promise for their use in integrated magneto-optic applications.

Keyword
bismuth iron garnet thin film, Faraday rotation, ferromagnetic resonance, magnetic anisotropy
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6463 (URN)10.1109/20.951201 (DOI)000170910900375 ()
Note
QC 20100922Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-12-14Bibliographically approved
2. Magnetic properties of single crystal film Bi3Fe5O12 prepared onto Sm3(Sc, Ga)5O12(111)
Open this publication in new window or tab >>Magnetic properties of single crystal film Bi3Fe5O12 prepared onto Sm3(Sc, Ga)5O12(111)
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2002 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 242, no Part 2, 775-777 p.Article in journal (Refereed) Published
Abstract [en]

Magnetic properties of single crystal Bi3Fe5O12 has been investigated in the temperature range between 2 and 670K. The Sm3(Sc,Ga)5O12 wafer has been used for substrates. Due to the small contribution of the substrate's magnetization, the film's magnetization can be clearly estimated to be 2040G (0K) and the Curie temperature has been estimated to be around 650K.

Keyword
Garnets—thin films, Saturation magnetization, Curie temperature, Sputtering—ion beam
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6464 (URN)10.1016/S0304-8853(01)01007-1 (DOI)000176868900043 ()
Note
QC 20100921Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-12-14Bibliographically approved
3. Determination of magnetic anisotropy constants for magnetic garnet epitaxial films using ferromagnetic resonance
Open this publication in new window or tab >>Determination of magnetic anisotropy constants for magnetic garnet epitaxial films using ferromagnetic resonance
2005 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 288, 15-21 p.Article in journal (Refereed) Published
Abstract [en]

The constants of magnetocrystalline anisotropy K-l and uniaxial anisotropy K-u are determined precisely by using ferromagnetic resonance (FMR) and a fitting procedure oil a (1 1 1) yttrium iron garnet (YIG) film made by pulsed laser deposition (PLD) technique. By applying a magnetic field in the azimuthal orientation we introduce measurement in a geometry which yields the anisotropy constants with a high accuracy. The new technique is compared with the previous analysis employing characteristic plane measurements. The new geometry yields at least 15% better accuracy in determining constant K, than by the previous method with FMR.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6465 (URN)10.1016/j.jmmm.2004.07.019 (DOI)000227480800002 ()2-s2.0-13544259556 (Scopus ID)
Note
QC 20111108. Updated from in Press to PublishedAvailable from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-12-14Bibliographically approved
4. Critical angles effect: Vanishing of cubic magnetocrystalline anisotropy in ferromagnetic resonance spectra
Open this publication in new window or tab >>Critical angles effect: Vanishing of cubic magnetocrystalline anisotropy in ferromagnetic resonance spectra
2002 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 10, 104419-1-104419-5 p.Article in journal (Refereed) Published
Abstract [en]

The shapes of ferromagnetic resonance (FMR) spectra of laser deposited epitaxial Y3Fe5O12 (YIG) films strongly depend on the orientation of the magnetic field with respect to the crystalline axes of the film. Strain and compositional inhomogeneties in the films define local magnetic anisotropies and could be responsible for the complexity of FMR spectra. We show that, in accordance with the Smit-Suhl formula, the contribution from a spatial distribution of the cubic magnetocrystalline anisotropy to the FMR spectra vanishes at certain orientations ("critical angles") of the magnetic field. We prove experimentally that it is a necessary condition to orient the magnetic field at the critical angles in order to measure single-line FMR spectra in an inhomogenous laser deposited YIG film.

Keyword
YTTRIUM-IRON-GARNET, LASER ABLATION, FILMS, DEPOSITION, MICROWAVE
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-6466 (URN)10.1103/PhysRevB.66.104419 (DOI)000178460900058 ()
Note
QC 20111121Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-12-14Bibliographically approved
5. Faraday rotation in two-dimensional magneto-optic photonic crystal
Open this publication in new window or tab >>Faraday rotation in two-dimensional magneto-optic photonic crystal
2005 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 253, no 1-3, 145-150 p.Article in journal (Refereed) Published
Abstract [en]

We study the enhancement of Faraday rotation in a two-dimensional square-lattice magneto-optic photonic crystal at optical wavelengths. We show that on incidence of a TM plane wave onto the magneto-optic photonic crystal, high TM-TE mode conversion takes place in the transmission bands of TM and TE fields. The photonic crystal structure increases the average wave path length, which in turn leads to a growth in the polarization rotation. We also show that associated with this phenomenon is a widening of the photonic crystal transmission band.

Keyword
Faraday rotation, Photonic band gap, Photonic crystals
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6467 (URN)10.1016/j.optcom.2005.04.064 (DOI)000231519600018 ()2-s2.0-23844478894 (Scopus ID)
Note
QC 20100914. Uppdaterad från Submitted till Published (20100914)Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-12-14Bibliographically approved
6. Faraday rotation in a two-dimensional photonic crystal with magneto-optic defect
Open this publication in new window or tab >>Faraday rotation in a two-dimensional photonic crystal with magneto-optic defect
2005 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 10, 1213-1215 p.Article in journal (Refereed) Published
Abstract [en]

We study the magneto-optic (MO) Faraday rotation in a two-dimensional square-lattice photonic crystal with a central MO defect layer in the optical wavelength range. We show that when a TM plane wave is incident upon a photonic crystal, an enhancement of Faraday rotation takes place in a region where a resonance peak appears in the photonic bandgap. In this region the mode conversion is high.

Keyword
Crystal lattices, Light reflection, Light transmission, Permittivity, Photons, Rotation
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6468 (URN)10.1364/OL.30.001213 (DOI)000229011800043 ()2-s2.0-20444429764 (Scopus ID)
Note
QC 20100914. Uppdaterad från Submitted till Published (20100914)Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-12-14Bibliographically approved

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