Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm

Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices.National Science Foundation (U.S.)Semiconductor Research Corporation. Function Accelerated nanoMaterial Engineerin

Temperature-dependent Faraday rotation and magnetization reorientation in cerium-substituted yttrium iron garnet thin films

We report on the temperature dependence of the magnetic and magneto-optical properties in cerium-substituted yttrium iron garnet (Ce: YIG) thin films. Measurements of the Faraday rotation as a function of temperature show that the magnetic easy axis of thin Ce: YIG films reorients from in-plane to out-of-plane on cooling below -100 degrees C. We argue that the temperature-dependence of the magnetostriction and magnetocrystalline anisotropy of Ce: YIG is the dominant factor contributing to the change in easy axis direction, and we describe the changes in the magneto-optical spectra with temperature.National Science Foundation (U.S.) (Award ECCS-1607865)United States. Defense Advanced Research Projects Agency (Award FA8650-16-1-7641

Magneto-Optical Thin Films for On-Chip Monolithic Integration of Non-Reciprocal Photonic Devices

Achieving monolithic integration of nonreciprocal photonic devices on semiconductor substrates has been long sought by the photonics research society. One way to achieve this goal is to deposit high quality magneto-optical oxide thin films on a semiconductor substrate. In this paper, we review our recent research activity on magneto-optical oxide thin films toward the goal of monolithic integration of nonreciprocal photonic devices on silicon. We demonstrate high Faraday rotation at telecommunication wavelengths in several novel magnetooptical oxide thin films including Co substituted CeO2−δ, Co- or Fe-substituted SrTiO3−δ, as well as polycrystalline garnets on silicon. Figures of merit of 3~4 deg/dB and 21 deg/dB are achieved in epitaxial Sr(Ti0.2Ga0.4Fe0.4)O3−δ and polycrystalline (CeY2)Fe5O12 films, respectively. We also demonstrate an optical isolator on silicon, based on a racetrack resonator using polycrystalline (CeY2)Fe5O12/silicon strip-loaded waveguides. Our work demonstrates that physical vapor deposited magneto-optical oxide thin films on silicon can achieve high Faraday rotation, low optical loss and high magneto-optical figure of merit, therefore enabling novel high-performance non-reciprocal photonic devices monolithically integrated on semiconductor substrates.National Science Foundation (U.S.). Division of Materials Research (Grant No. DMR 0604430)National Science Foundation (U.S.). Division of Materials Research (Grant No. 1231392, Electronic, Photonic, and Magnetic Devices Program

Magnetism and Faraday Rotation in Oxygen-Deficient Polycrystalline and Single-Crystal Iron-Substituted Strontium Titanate

Both polycrystalline and single-crystal films of iron-substituted strontium titanate, Sr(Ti[subscript 0.65]Fe[subscript 0.35])O[subscript 3−δ], prepared by pulsed laser deposition, show room-temperature magnetism and Faraday rotation, with the polycrystalline films exhibiting higher saturation magnetization and Faraday rotation. The magnetic properties vary with the oxygen pressure at which the films are grown, showing a maximum at pressures of approximately 4  μ Torr at which the unit-cell volume is largest. The results are discussed in terms of the oxygen stoichiometry and corresponding Fe valence states, the structure and strain state, and the presence of small-volume fractions of metallic Fe in single-crystal films grown at the optimum deposition pressure. Integration of magneto-optical polycrystalline films on an optical-waveguide device demonstrates a nonreciprocal phase shift.National Science Foundation (U.S.) (Grants DMR1419807 and ECCS1607865)Semiconductor Research Corporation. Function Accelerated nanoMaterial Engineerin

Magnetic oxides

Written by a leading researcher in the magnetics communityContemporary and authoritative treatise with emphasis on physics and chemistry of local molecular interaction

Paramagnetic resonance and relaxation of Ti3+ in rubidium alum.

The paramagnetic resonance spectrum of the rare Ti3+ ion in cubic RbAl(SO4)2. 12H20 has been investigated with an X-band microwave spectrometer at liquid helium temperatures. Spectra were plotted for the d-c magnetic field rotated in the {100} and {011} planes and twelve resonance lines were observed. By considering a model of twelve magnetic complexes, three different g-factors have been determined, 1.895 +/- .002, 1.715 +/- .002 and 1.767 +/- .002, which result from a crystal electric field of orthorhombic symmetry. Through the application of group theory and quantum mechanical perturbation methods, crystal field energy levels have been calculated to be 1050 cm.-1, 1320 cm.-1 and 20,300 cm.-1 above the ground state, with the last value fitting the result of an optical spectroscopic experiment with Ti3+ in a similar environment. Spin-lattice relaxation measurements were made between 4. 2 °K and 1.6 °K and the relaxation time T1 was found to vary from 3. 3 msec. to 63 msec. over this temperature range. From the nature of the temperature dependence, it is evident that the Raman process is dominant at 4.2°K, as theoretical calculations have predicted. The concentration of titanium substituted for aluminum in the crystals studied has been estimated to be 0.02 per cent

Structure, magnetic properties and magnetoelastic anisotropy in epitaxial Sr(Ti₁₋ₓCoₓ)O₃ films

We report the structure, magnetic properties and magnetoelastic anisotropy of epitaxial Sr(Ti₁₋ₓCoₓ)O₃ films grown on LaAlO₃ (001) and SrTiO₃ (001) substrates by pulsed laser deposition. Room temperature ferromagnetism was observed in the Sr(Ti[subscript 0.86]Co[subscript 0.14])O₃ and Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ films. The formation of magnetic secondary phases such as Co-metal clusters in Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ is excluded based on x-ray diffraction, cross-sectional TEM, x-ray photoelectron spectroscopy and x-ray-absorption near edge spectroscopy. A large magnetic anisotropy is observed in Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ films. The net anisotropy is strongly influenced by growth conditions and the substrate and is attributed to magnetoelastic effects. The magnetoelastic anisotropy is related to the valence and spin states of the Co ions, which contribute to the ferromagnetic properties. Magneto-optical characterization yields a figure of merit (Faraday rotation/optical absorption) of 0.57 deg dB⁻[superscript 1] in the Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ film at 1550 nm wavelength, making it potentially useful in integrated magneto-optical applications.National Science Foundation (U.S.)National Science Foundation (U.S.) (Division of Materials Research)Korea Research Foundation (Grant MOEHRD)Korea (South). Ministry of Government Administration (KRF-2006-352-D00094

Voltage tunable microwave ferrite resonator

A novel method of implementing a tunable resonator using an applied voltage is presented. Stress is used to tune a microstrip resonator fabricated on a polycrystalline ferrite substrate. The stress was applied either mechanically with screws or electronically using piezoelectric actuators. We have demonstrated tunability of 300 MHz using screws and 50 MHz using a piezoelectric actuator at a center frequency of 2.3 GHz. Explanation of the tuning method is given and means to extend the tuning range is discussed. This method opens the possibility of compact low-power tunable filters with wide tuning range at microwave frequencies.United States. Dept. of the Air Forc

Magnetoelastic effects in SrTi1−xMxO3 (M = Fe, Co, or Cr) epitaxial thin films

SrTi[subscript 1−x]M[subscript x]O[subscript 3] films in which M = Fe, Co, or Cr and x=0.04–0.5 have been grown epitaxially on CeO[subscript 2]-buffered Si, SrTiO[subscript 3], and LaAlO3 substrates. Films grown in vacuum containing Fe or Co typically showed a strong uniaxial magnetic anisotropy in the out-of-plane direction, a saturation moment on the order of 0.5μ[subscript B]/Fe or Co, and a magnetization that persists to temperatures of order 1000 K. In contrast, films containing Cr showed no evidence of a spontaneous magnetic moment. The films are typically in a high in-plane compressive strain state due to epitaxial growth. The results are discussed in terms of the magnetoelastic effects from specific ionic valence states, and the magnetization versus temperature curves are fitted to a model for magnetoelastic spin ordering.National Science Foundation (U.S.). Division of Materials ResearchSamsung ElectronicsIntel CorporationChinese Scholarship Counci