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Pulsed laser deposited Y3Fe5O12 films: Nature of magnetic anisotropy II
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
2010 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 1, 013902- p.Article in journal (Refereed) Published
Abstract [en]

Recently we found epitaxial Fe-deficient yttrium iron garnet Y3Fe5-tO12-3t/2 (YIG) films pulsed laser deposited onto the (111) and (001) face of Gd3Ga5O12 single crystal experience, respectively, strong rhombohedral and tetragonal distortions and possess unusual magnetic anisotropy. Using the crystal field theory, we explained these anomalies and showed in YIG (111) films ferric ion vacancies preferentially occupy octahedral complexes, order themselves along the [111] growth direction, cause rhombohedral lattice distortions, generate strong uniaxial and significantly reduce cubic crystalline anisotropy, Manuilov et al., [J. Appl. Phys. 106, 123917 (2009)]. Oxygen vacancies govern electrical neutrality and in spite of high concentration (in access of 7 at. %) they are perfectly ordered that is indicated by narrow ferromagnetic resonance linewidth. The present paper aims to compare growth anisotropies induced in (111) and (001) epitaxial Fe-deficient YIG films. Ordering of vacancies appeared to be different in (111) and (001) oriented YIG films. In highly Fe-deficient YIG (001) we found much smaller imbalance in redistribution of vacancies between the octa-and tetrahedral magnetic sublattices. This feature together with a weaker crystal field in tetrahedral Fe3+-O2- complexes result in reduced growth induced magnetic anisotropy in (001) oriented tetragonal distorted YIGs compared to rhombohedral distorted YIG (111) films.

Place, publisher, year, edition, pages
2010. Vol. 108, no 1, 013902- p.
Keyword [en]
IRON-GARNET FILMS, GROWTH-INDUCED ANISOTROPY, FERROMAGNETIC-RESONANCE, YIG-FILMS
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
URN: urn:nbn:se:kth:diva-29462DOI: 10.1063/1.3446840ISI: 000280000400054Scopus ID: 2-s2.0-77955210310OAI: oai:DiVA.org:kth-29462DiVA: diva2:395923
Funder
Swedish Research Council
Note
QC 20110208Available from: 2011-02-08 Created: 2011-02-02 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Ferromagnetic resonance in films with growth induced anisotropy
Open this publication in new window or tab >>Ferromagnetic resonance in films with growth induced anisotropy
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis discusses two different magnetic materials: epitaxial yttrium iron garnet (YIG) and heteromorphous CoFeB-SiO2 films.

YIG films were grown by pulse laser deposition (PLD) techniques onto gadolinium gallium garnet (GGG) substrates of (111) and (001) crystal orientations. Using stoichiometric and overstoichiometric ablative targets, we developed two types of YIG submicron films. The films grown from overstoichiometric targets have magnetic properties slightly different from standard liquid phase epitaxy (LPE) YIGs. They also demonstrate good substrate matching and approximately 6% nonstoichiometry. In contrary, films grown from stoichiometric targets posses surprisingly high values of uniaxial anisotropy, meanwhile cubic anisotropy is reduced several times. These films also reveal strong lattice distortions and nonstoichiometry around 17%.

Employing Weiss molecular field theory and single-ion anisotropy model we determined the preferential occupancy of the octahedral [a] positions in the YIG cubic lattices by Fe3+ vacancies. The vacancies were found to be preferentially oriented along the growth direction perpendicular to the film surface. We called this effect “deformation blockade”.

Different magnetostatic surface wave (MSSW) filters were also demonstrated. The filters employ high uniaxial anisotropy in YIG submicron films with magnetic losses ΔH ~ 1 Oe.

 Heteromorphous CoFeB-SiO2 films were deposited onto glass substrates employing carrousel magnetron sputtering. This novel technique allows amorphous films fabrication with record high in-plane anisotropy. The induced anisotropy fields here are approximately dozen times greater the values achieved using conventional growth technique when external bias field is applied during deposition process.

Interesting observations were made studying CoFeB-SiO2 magnetization dynamics in the wide frequency range from 500 kHz up to 15 GHz.  Two different anomalies of the magnetic susceptibility were found at the field of in-plane anisotropy Hp and critical field Hcr (0 < Hcr < Hp). We explained the anomalies appearance by sequence of the domain walls transformations so that Néel-Bloch-Néel domain wall transition stands for the instability at H = ±Hcr and transition from the uniformly magnetized state to the domain state with Néel domain wall and vice versa is responsible for the instability at H = ±Hp.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xv, 114 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2011:16
Keyword
ferromagnetic resonance, magnetic anisotropy, single-ion anisotropy model, ferrites, magnetic epitaxial films, magnetostatic waves, pulsed laser deposition, magnetic alloys, domains, domain wall transformations
National Category
Condensed Matter Physics Other Electrical Engineering, Electronic Engineering, Information Engineering Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-48248 (URN)978-91-7501-193-6 (ISBN)
Public defence
2011-12-14, Ka-C2, KTH-Electrum, Isafjordsgatan 26, Kista, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note
QC 20111122Available from: 2011-11-22 Created: 2011-11-16 Last updated: 2011-11-22Bibliographically approved

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