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1.
In SrCeO3 the oxygen vacancy concentration at elevated temperatures depends on the oxygen partial pressure in the surrounding atmosphere. Changes of the oxygen vacancy concentration are accompanied by change in the hole concentration and therefore can be measured by electrical conductivity measurements. We apply a dynamic method for studying the diffusion of oxygen vacancies by measurements of the time dependence of the electrical conduction after a sudden change in the oxygen partial pressure has taken place. In doped samples and under wet conditions the protonic charge carriers are mainly incorporated by a dissociative absorption of water and lead to a noticeable protonic conduction. The proton diffusion in SrCe0.95 Y0.05O3 is determined by relaxation measurements at a polarised sample in wet and hydrogen containing atmosphere. The electrochemical cell discussed here is characterised by a combination of one reversible and one (hydrogen) ion blocking electrode. From the time dependence of the depolarisation process the hydrogen diffusivity is extracted. 相似文献
2.
The d.c. conductivity and Seebeck coefficient of Ca and Mg doped YIG have been measured at 1200–1700 K. A change of p-type to n-type conductivity was accomplished by varying the oxygen pressure between 1 and 10-8 atm. From the position of the conductivity minimum as a function of temperature the band gap energy is estimated to be 2.85 eV. 相似文献
3.
Mössbauer spectroscopy of a silicon substituted YIG containing 0.3 Si4+ per formula unit has shown that a spin reorientation, from [111] to [100], occurs between 265 and 80 K. The transitions occur by way of the magnetic space groups . The broad spin reorientation is mainly a consequence of the persistence of a nonuniform distribution of Fe2+ ions over the octahedral sites. 相似文献
4.
The extremely low thermal conductivity at low temperatures of some yttrium iron garnet single crystals is attributed to sheets of defects revealed by chemical etching. 相似文献
5.
C. J. M. Denissen 《Hyperfine Interactions》1990,56(1-4):1577-1585
57Fe-enriched, epitaxial Y3Fe5O12 films have been implanted with 50 keV and 100 keV neon ions with a dose of 4·1014Ne+/cm2. Depth-selective conversion electron Mössbauer spectroscopy has been performed at 300 K and 40 K. The results show that the 50 keV-implanted sample can be interpreted as an amorphous layer on top of an almost unperturbed YIG layer. In the 100 keV-implanted film a buried amorphous layer is observed. 相似文献
6.
7.
S. I. Yushchuk 《Technical Physics》1999,44(12):1454-1456
The layered structure of yttrium iron garnet films, ranging in thickness from 0.7 to 4.1 μm, grown epitaxially on single-crystal
gallium-gadolinium garnet substrates, was investigated by x-ray spectral microanalysis. The ferrite films were chemically
etched layer by layer in a mixture of orthophosphoric and sulfuric acids at T=353–423 K. It was established that the chemical composition of the films varies over the thickness because of the nonuniform
distribution of gadolinium, gallium, lead, and platinum ions; the film-substrate transitional layer and the surface layer
of the film differ most greatly with respect to the composition and magnetic properties. It was shown that the thickness of
the transitional layers and their negative effect on the magnetic characteristics of ferrite films decrease appreciably if
at the time of immersion of the substrate and pulling of epitaxial structure out of the fluxed solution the substrate holder
together with a special mixer rotate at a rate of 50 rpm and the pulling velocity is 20 cm/min.
Zh. Tekh. Fiz. 69, 62–64 (December 1999) 相似文献
8.
Samuel M. Myers Horst Meyer
J. P. Remeika
《Journal of Physics and Chemistry of Solids》1969,30(12):2687-2692Pulse measurements of T1 for 57Fe nuclei in very pure, single crystals of YIG are reported. The temperature was varied from 2° to 292°K, and the externally applied field ranged from 0 to 6000 Oe. The temperature variation of T1 is quite strong, being three orders of magnitude in the range 2°–40°K. At constant temperature, T1 changed approximately one order of magnitude between saturation field and 6000 Oe. The data are compared with the results of a calculation by Beeman and Pincus, in which a second-order Raman process and the three-magnon process are assumed to predominate below 50°K. Agreement is only qualitative, the experimental values of T1 being larger than predicted. At 4.2°K in zero field, it is found that a polycrystalline sample containing particles of ≈ 5 × 10−4 cm dia. has a value of 1/T1 which is some two orders of magnitude larger than for a macroscopic crystal. The presence of a relaxation mechanism associated with surface effects is suggested. 相似文献
9.
10.
Yongxue He Peng He Soack Dae Yoon P.V. Parimi F.J. Rachford V.G. Harris C. Vittoria 《Journal of magnetism and magnetic materials》2007
A magnetic field tunable, broadband, low-loss, negative refractive index metamaterial is fabricated using yttrium iron garnet (YIG) and a periodic array of copper wires. The tunability is demonstrated from 18 to 23 GHz under an applied magnetic field with a figure of merit of 4.2 GHz/kOe. The tuning bandwidth is measured to be 5 GHz compared to 0.9 GHz for fixed field. We measure a minimum insertion loss of 4 dB (or 5.7 dB/cm) at 22.3 GHz. The measured negative refractive index bandwidth is 0.9 GHz compared to 0.5 GHz calculated by the transfer function matrix theory and 1 GHz calculated by finite element simulation. 相似文献
11.
The magnetic HFI of cerium ion in a lanthanum-doped yttrium iron garnet is investigated by the gamma-gamma angular correlation technique. It is found that cerium, formed after radioactive decay of La140, reaches the ground state of Ce3+ in a time short compared with the nuclear state life-time of 4.9 nsec. Quasi-static as well as time-dependent interactions are detected, yielding an internal field ofH eff=(21.5± 3) kOe at the nuclei of cerium. The molecular field theory is applied in the analysis of data, and values for the exchange field, the spinlattice relaxation time and the magnectic moment of cerium ion in an iron garnet at room temperature are deduced. These values are:H exch=(147±20)kOe, τ c =(4.5±0.6)×10?13 sec and 〈μz〉=(0.017±0.002) Bohr magnetons. 相似文献
12.
E. Popova N. Keller F. Jomard L. Thomas M.-C. Brianso F. Gendron M. Guyot M. Tessier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):69-74
Magnetic exchange coupling has been observed for ultrathin films of yttrium iron garnet (Y3Fe5O12 or YIG). Single-crystalline YIG films were prepared on yttrium aluminium garnet (Y3Al5O12 or YAG) substrates by pulsed laser deposition. (111) and (110) oriented substrates were used. Film thicknesses were varied
from 180 ? to 4600 ?. Epitaxial growth of YIG on YAG was obtained in spite of the lattice mismatch of 3%. Magnetic hysteresis
loops recorded for ultrathin YIG films have a “bee-waist” shape and show a coupling between two different magnetic phases.
The first phase is magnetically soft YIG. A composition study by secondary ion mass spectroscopy shows the second phase to
be Y3Fe5-xAlxO12 due to the interdiffusion of Fe and Al at the film/substrate interface. This compound is known to be magnetically harder
and to have weaker magnetization than YIG. The coupling of the two phases leads to a hysteresis loop displacement at low temperatures.
This displacement varies differently with film thickness for two substrate orientations. Assuming an interfacial coupling,
the maximal interaction energy is estimated to be about 0.17 erg/cm2 at 5 K for (111) oriented sample.
Received 3 June 2002 / Received in final form 7 October 2002 Published online 27 January 2003
RID="a"
ID="a"Presently at LPM, Université H. Poincaré, BP 239, 54506 Vandœuvre-lès-Nancy e-mail: popova@lpm.u-nancy.fr 相似文献
13.
Magnetic bubbles have again become a subject of significant attention following the experimental observation of topologically nontrivial magnetic skyrmions. In recent work, tailoring the shape of the bubbles is considered a key factor for their dynamics in spintronic devices. In addition to the reported circular, elliptical, and square bubbles, here we observe triangular bubble domains in bismuth-doped yttrium iron garnet(Bi-YIG) using Kerr microscopy. The bubble domains evolve from discrete cir... 相似文献
14.
M. Bonnet A. Delapalme H. Fuess P. Becker 《Journal of Physics and Chemistry of Solids》1979,40(11):863-876
Magnetic structure amplitudes of 170 reflections up to sin were measured by polarized neutron diffraction at T = 295K on yttrium iron garnet. The data set was completed by model calculations and the magnetization density was determined. The magnetic moments obtained by integration and refinement are considerably reduced on both iron sites due to charge density transferred from intervening ligand ions. A residual moment of uncancelled spin of (0.032 ±0.004) μB is observed on the oxygen ion. Evidence for magnetization density on the oxygen atom and between oxygen and tetrahedral iron was found. A qualitative discussion in terms of a molecular orbital model is given. A further data set collected at 4.2K showed equally a magnetic moment lower than expected for the free ion. 相似文献
15.
16.
B.?A.?Gizhevski? Yu.?P.?Sukhorukov E.?A.?Gan’shina N.?N.?Loshkareva A.?V.?Telegin N.?I.?Lobachevskaya V.?S.?Gaviko V.?P.?Pilyugin 《Physics of the Solid State》2009,51(9):1836-1842
Bulk dense samples of nanostructured yttrium iron garnet Y3Fe5O12 with crystallite sizes of 20–40 nm are prepared by high-pressure torsion from a garnet powder with micron grains. The absorption
and Faraday rotation spectra in the IR range and the transverse Kerr effect spectra in the visible spectral range for these
samples are measured. The absorption and magneto-optical effect spectra are in agreement with the corresponding spectra of
single crystals. The appearance of additional absorption bands at 2 and 3 μm is associated with the violation of the stoichiometry
of the nanogarnet and the possible contamination of the initial material. The specific Faraday rotation in the transparency
window is approximately 1.5 times smaller than the corresponding quantity for single crystals. The extrema in the Kerr effect
spectra coincide with those for single crystals, are smaller in magnitude, and are smeared. On the whole, the prepared bulk
samples are transparent in the IR spectral range and exhibit optical and magneto-optical characteristics comparable to the
corresponding parameters for single crystals. The high density of point defects of the nanogarnet is primarily due to the
violation of the stoichiometry and the valence state of iron ions. 相似文献
17.
V. F. Shkar’ E. I. Nikolaev V. N. Sayapin A. I. Linnik V. P. Denysenkov A. M. Grishin S. I. Khartsev 《Physics of the Solid State》2005,47(6):1107-1110
Ferromagnetic resonance (FMR) and vibrating-sample magnetometer techniques were used to study the nature of the structural characteristics of yttrium iron garnet films deposited through either liquid phase epitaxy or laser evaporation on a (111)-oriented gallium gadolinium garnet substrate. It was proved that, based on the experimentally observed cubic magnetic anisotropy, deposited films should be considered to be single crystals. However, the absence of the FMR domain branch in a nonsaturated film and the shape of the magnetization curve indicate that a deposited film when demagnetized does not have a domain structure, as would be expected for a single-crystal film. According to the model proposed, a deposited film consists of close-packed single-crystal fragments with equal crystallographic orientation, the boundaries between which are in a partially atomically disordered state. As a result, such a film is both locally and macroscopically anisotropic, like a continuous single crystal. This film can split into domains only within a fragment (as is the case in a magnetic granular polycrystal); however, this does not happen, because the linear dimensions of a submicroscopic fragment are smaller than the equilibrium domain width. 相似文献
18.
Structure dependence of magnetic properties in yttrium iron garnet by metal-organic decomposition method
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The yttrium iron garnet(YIG) samples are prepared at different temperatures from 900?C to 1300?C by the metalorganic decomposition(MOD) method. The chemical composition and crystal structure of the samples are studied by scanning electron microscope(SEM), XRD, and M ¨ossbauer spectrometer. It is shown that the ratio of ferric ions on two types of sites, the octahedral and the tetrahedral, is increased with the sintering temperature. At 1300?C, the pure garnet phase has been obtained, in which the ferric ions ratio is 2:3 leading to the minimum magnetic coercivity and maximum saturation magnetization. These results provide a route to synthesize pure YIG materials as the basic materials used in various spintronics applications. 相似文献
19.
Brillouin scattering measurements on yttrium iron garnet (YIG) have revealed the scattering due to thermal acoustic magnons. The intensity and frequency shift of the magnon peaks as a function of applied magnetic field and incident light wavelength have been investigated and are discussed here within the framework of a simple light scattering theory. 相似文献