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1.
Effect of Bi-substitution on the dielectric properties of polycrystalline yttrium iron garnet 总被引:8,自引:0,他引:8
Hongjie Zhao Ji Zhou Yang Bai Zhilun Gui Longtu Li 《Journal of magnetism and magnetic materials》2004,280(2-3):208-213
The effect of Bi-substitution on the dielectric properties of yttrium iron garnet (YIG) was studied in this paper. The Bi-substituted YIG (YIG:Bi) polycrystalline samples, having composition of Y3−xBixFe5O12, were prepared by the solid-state reaction method. x varied from 0 to 1.2. The phase formation and microstructure were performed by X-ray diffraction and scanning electron microscopy, respectively. Ions valency was identified by X-ray photoelectron spectroscopy. The impedance analyzers are used to measure the frequency dependence and the temperature dependence of relative dielectric constant (r) and loss tangent (tan δ). The experimental results show that the Bi-substitution lowers the phase formation and sintering temperature. Electronic carrier concentration drops dramatically due to limitation of ferric valency variation. Hence, r and tan δ decrease with addition of Bi. Dispersion characteristic indicates non-Debye-type dispersion. A maximum of r appears as the temperature rises. 相似文献
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3.
N. Rodziah M. Hashim I.R. IdzaI. Ismayadi A.N. HapishahM.A. Khamirul 《Applied Surface Science》2012,258(7):2679-2685
The microstructure evolution in several polycrystalline yttrium iron garnet samples as a result of a sintering scheme was studied in detail, in parallel with the changes in their magnetic properties. Samples with nanometer sized starting powder were synthesized by employing the High-Energy Ball Milling technique and then sintering toroidal compacts of the milled powder. Nine sintered samples were obtained, each corresponding to a particular sintering from 600 °C to 1400 °C. The samples were characterized for their evolution in crystalline phases, microstructure and magnetic hysteresis-loops parameters. The results showed an increasing tendency of the saturation magnetization and saturation induction with grain size, which is attributed to crystallinity increase and to reduction of demagnetizing fields in the grains. The variation in coercivity could be related to anisotropy field changes within the samples due to grain size changes. In particular, the starting appearance of room temperature ferromagnetic order suggested by the sigmoid-shaped B-H loops seems to be dependent on a sufficient number of large enough magnetic domain-containing grains having been formed in the microstructure. Viewed simultaneously, the hysteresis loops appear to belong to three groups with different magnetism-type dominance, respectively dependent on phase purity and three different groups of grain size distributions. 相似文献
4.
V. Saraswati M.S. Multani V.R. Palkar R. Vijayaraghavan A. Gurjar 《Journal of magnetism and magnetic materials》1984,43(3):256-260
Polycrystalline ceramic YIG has been synthesized with submicron microstructure. The log-log plot of FMR linewidth versus average grain size gives a power law dependence α-10 where α0 is the average grain size. The instability threshold hcrit for increasing magnetic field vector of the microwave parallel pump shows a linear log-log dependence with average grain size. 相似文献
5.
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
6.
Shuyao Chen 《中国物理 B》2022,31(4):48503-048503
Yttrium iron garnet (YIG) films possessing both perpendicular magnetic anisotropy (PMA) and low damping would serve as ideal candidates for high-speed energy-efficient spintronic and magnonic devices. However, it is still challenging to achieve PMA in YIG films thicker than 20 nm, which is a major bottleneck for their development. In this work, we demonstrate that this problem can be solved by using substrates with moderate lattice mismatch with YIG so as to suppress the excessive strain-induced stress release as increasing the YIG thickness. After carefully optimizing the growth and annealing conditions, we have achieved out-of-plane spontaneous magnetization in YIG films grown on sGGG substrates, even when they are as thick as 50 nm. Furthermore, ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements further verify the good spin transparency at the surface of our YIG films. 相似文献
7.
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
8.
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
9.
Crystal growth and the magnetic properties of bismuth substituted yttrium iron garnet (Bi-YIG) nanoparticles were studied with particular focus on the bismuth composition dependence of the magnetic properties of the particles and the effects of annealing on the garnet phase formation. The Bi-YIG nanoparticles of 47–67 nm in size can be chemically synthesized when they are annealed at 650–850 °C. Both the lattice constant and the magnetization of the garnet nanoparticles linearly increase when the bismuth composition in the Bi-YIG particles increases. We have found that chemically synthesized nanoparticles transform from the amorphous to the garnet phase when annealed at temperatures below 650 °C, while the onset of magnetic moment of iron in the garnet nanoparticles is observed slightly above 650 °C. According to Mössbauer effect measurements, the hyperfine fields of 57Fe at the tetrahedral and octahedral sites in the garnet are 39 and 48 T, respectively. 相似文献
10.
Effects of Bi substitution upon magnetic and magnetodielectric properties of Y3Fe5O12 ceramics were investigated. It was found that the saturation magnetization decreases and the magnetic ordering temperature increases as the amount of Bi increases. The contribution of intrinsic and extrinsic effects to magnetodielectric effects decreases with increase of Bi, which results in the decrease of magnetodielectric coefficient of Y3−xBixFe5O12 ceramics. 相似文献
11.
This paper focuses on the magnetic, structural and thermal properties of mechanically alloyed Y2O3/α-Fe2O3 mixed powders and investigates the effects of the mechanical milling and heat treatment on the synthesis of yttrium iron garnet from the primary materials. The morphological and structural studies were carried out by scanning electron microscope and X-ray diffraction, respectively. The thermal activities were measured by differential thermal analysis. The magnetic properties were studied by vibrating sample magnetometer. The results showed that high-energy milling does not lead to the garnet formation and even does not decrease the temperature of the garnet formation. Furthermore, the orthoferrite phase can be achieved slightly during the milling process (up to 96 h) and completely by the heat treatment at lower temperatures (850 °C). 相似文献
12.
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
13.
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
14.
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
15.
V. E. Zubov A. D. Kudakov N. L. Levshin M. A. Vlasov 《Journal of Experimental and Theoretical Physics》2013,116(5):766-774
The reversible change in the domain structure and the magnetic domain width in bismuth-containing iron garnet films with an easy magnetization axis oriented normal to their surface during adsorption caused by hydrogen bonds is studied by a magnetooptical method. The dependence of the domain width on the vapor pressure of methyl alcohol or water in a cell with a sample is determined, and the time dependence of the domain width induced by the adsorption-desorption processes occurring between methyl alcohol molecules or water molecules on the film surface is studied. A model is proposed to explain the detected effects. 相似文献
16.
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
17.
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
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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
20.
A. Rogalev F. Wilhelm A. Yaresko M.V. Indenbom 《Journal of magnetism and magnetic materials》2009,321(23):3945-3962
X-ray magnetic circular dichroism (XMCD) was used to probe the existence of induced magnetic moments in yttrium iron garnet (YIG) films in which yttrium is partly substituted with lanthanum, lutetium or bismuth. Spin polarization of the 4d states of yttrium and of the 5d states of lanthanum or lutetium was clearly demonstrated. Angular momentum resolved d-DOS of yttrium and lanthanun was shown to be split by the crystal field, the two resolved substructures having opposite magnetic polarization. The existence of a weak orbital moment involving the 6p states of bismuth was definitely established with the detection of a small XMCD signal at the Bi M1-edge. Difference spectra also enhanced the visibility of subtle changes in the Fe K-edge XMCD spectra of YIG and {Y, Bi}IG films. Weak natural X-ray linear dichroism signatures were systematically observed with all iron garnet films and with a bulk YIG single crystal cut parallel to the (1 1 1) plane: this proved that, at room temperature, the crystal cannot satisfy all requirements of perfect cubic symmetry (space group: ), crystal distortions preserving at best trigonal symmetry ( or R3m). For the first time, a very weak X-ray magnetic linear dichroism (XMLD) was also measured in the iron K-edge pre-peak of YIG and revealed the presence of a tiny electric quadrupole moment in the ground-state charge distribution of iron atoms. Band-structure calculations carried out with fully relativistic LMTO-LSDA methods support our interpretation that ferrimagnetically coupled spins at the iron sites induce a spin polarization of the yttrium d-DOS and reproduce the observed crystal field splitting of the XMCD signal. 相似文献