16 research outputs found
Faraday rotation spectra of bismuth-substituted ferrite garnet films with in-plane magnetization
Single crystalline films of bismuth-substituted ferrite garnets have been
synthesized by the liquid phase epitaxy method where GGG substrates are dipped
into the flux. The growth parameters are controlled to obtain films with
in-plane magnetization and virtually no domain activity, which makes them
excellently suited for magnetooptic imaging. The Faraday rotation spectra were
measured across the visible range of wavelengths. To interprete the spectra we
present a simple model based on the existence of two optical transitions of
diamagnetic character, one tetrahedral and one octahedral. We find excellent
agreement between the model and our experimental results for photon energies
between 1.77 and 2.53 eV, corresponding to wavelengths between 700 and 490 nm.
It is shown that the Faraday rotation changes significantly with the amount of
substituted gallium and bismuth. Furthermore, the experimental results suggest
that the magnetooptic response changes linearly with the bismuth substitution.Comment: 15 pages, 6 figures, published in Phys. Rev.
Oxygen partial pressure dependence of magnetic, optical and magneto-optical properties of epitaxial cobalt-substituted SrTiO3 films
Cobalt-substituted SrTiO3 films (SrTi0.70Co0.30O3-δ) were grown on SrTiO3 substrates using pulsed laser deposition under oxygen pressures ranging from 1 μTorr to 20 mTorr. The effect of oxygen pressure on structural, magnetic, optical, and magneto-optical properties of the films was investigated. The film grown at 3 μTorr has the highest Faraday rotation (FR) and magnetic saturation moment (Ms). Increasing oxygen pressure during growth reduced Ms, FR and optical absorption in the nearinfrared. This trend is attributed to decreasing Co2+ ion concentration and oxygen vacancy concentration with higher oxygen partial pressure during growth. © 2015 Optical Society of America
Small-polaron hopping conductivity in bilayer manganite LaSrMnO
We report anisotropic resistivity measurements on a
LaSrMnO single crystal over a temperature range
from 2 to 400 K and in magnetic fields up to 14 T. For K, the
temperature dependence of the zero-field in-plane resistivity
obeys the adiabatic small polaron hopping mechanism, while the out-of-plane
resistivity can be ascribed by an Arrhenius law with the same
activation energy. Considering the magnetic character of the polarons and the
close correlation between the resistivity and magnetization, we developed a
model which allows the determination of . The excellent
agreement of the calculations with the measurements indicates that small
polarons play an essential role in the electrical transport properties in the
paramagnetic phase of bilayer manganites.Comment: 4 pages, 3 figures, to appear in Physical Review
Strategies for Controlled Placement of Nanoscale Building Blocks
The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others
Microwave Ferrites for Cryogenic Applications
Recent advances in microwave ferrite device technology have seen the introduction of superconductivity that virtually eliminates insertion losses due to electrical conduction in microstrip circuits. The conventional ferrimagnetic spinel and garnet compositions, however, are not generally optimized for temperatures in the vicinity of 77 K and may require chemical redesign in order to realize the full potential of these devices. For microwave transmission, absorption losses may be reduced by a natural lengthening of the spin-lattice relaxation time and the suppression of hopping electron activity at low temperatures. However, these properties could be degraded by fast-relaxing impurities that broaden ferrimagnetic resonance lines. At low temperatures, saturation magnetizations increase according to the Brillouin-Weiss function behavior that is characteristic of most magnetic materials. Increased magnetocrystalline anisotropy energies will produce greater coercive fields that will lead directly to higher hysteresis loop switching energies. Other parameters that are influenced adversely by reduced temperatures are the magnetostriction constants, which can cause significant deterioration in the stability of the remanence ratios of hysteresis loops. To modify room temperature ferrites for devices that use high-Tc superconductors, magnetochemistry must be applied to obtain the desired parameter values, which in turn must be chosen through design tradeoffs and are set by the performance requirements of particular device applications