共查询到20条相似文献,搜索用时 15 毫秒
1.
The effect of high pressures up to 70 GPa on single-and polycrystalline samples of yttrium iron garnet Y357Fe5O12 is studied by Mössbauer absorption spectroscopy (for the 57Fe nucleus) in a diamond-anvil cell. It is found that the hyperfine magnetic field Hhf at 57Fe nuclei vanishes abruptly at a pressure of 48 ± 2 GPa, which indicates the transition of the crystal from the ferrimagnetic state to nonmagnetic one. The magnetic transition is irreversible. When the pressure decreases, the magnetic state is not recovered and the garnet remains nonmagnetic until zero pressure. The behavior of the quadrupole splitting and isomer shift shows that, simultaneously with the magnetic transition, irreversible electron and possibly spin transitions occur with changes in the local crystalline structure. The mechanisms of the magnetic collapse are discussed. 相似文献
2.
K. Araki T. Goto Y. Nemoto T. Yanagisawa B. Lüthi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):257-259
The temperature dependence of the elastic constants in
Tb3Ga5O12 was measured and analysed with a simple crystal
field model. The magneto-elastic coupling constants have been deduced from
this experiment. The coupling constant gΓ5, related to the
c44 mode, is anomalously large. These coupling constants are important
for the interpretation of the phonon Hall effect. 相似文献
3.
U. V. Valiev J. B. Gruber D. K. Sardar A. K. Mukhammadiev Sh. A. Rakhimov V. Yu. Sokolov 《Optics and Spectroscopy》2007,102(6):910-917
The spectra of magnetic circular dichroism in the range of the 7 F 6→5 D 4 absorption band and the spectra of magnetic circular polarization of luminescence in the range of the 5 D 4→7 F 5 band in the terbium-gallium garnet Tb3Ga5O12 are studied at a temperature of 80 K. The optical transitions between the Stark sublevels of the 7 F 6, 7 F 5, and 5 D 4 multiplets are identified based on the analysis of the magneto-optical and optical spectra. It is shown that the experimentally determined symmetry and energy of the Stark sublevels of these multiplets confirm the results of numerical calculations of the energy spectrum of the Tb3+ rare-earth ion in terbium-gallium garnet. 相似文献
4.
M. S. B. Darby T. C. May-Smith R. W. Eason 《Applied Physics A: Materials Science & Processing》2008,93(2):477-481
We have demonstrated pulsed laser deposition of Nd-doped gadolinium gallium garnet on Y3Al5O12 by the simultaneous ablation of two separate targets of Nd:Gd3Ga5O12 (GGG) and Ga2O3. Such an approach is of interest as a method of achieving stoichiometry control over films whilst the growth parameters are
kept constant and optimal for high quality crystal growth. We show here how the stoichiometry and resultant lattice parameter
of a film can be controlled by changing the relative deposition rates from the two targets. Films have been grown with enough
extra Ga to compensate for the deficiency that commonly occurs when depositing only from a GGG target. We have also grown
crystalline GGG films with an enriched Ga concentration, and this unconventional approach to film stoichiometry control may
have potential applications in the fabrication of films with advanced compositionally graded structures. 相似文献
5.
The magnetocaloric effect and the Faraday rotation in a paramagnetic cubic crystal of terbium gallium garnet in strong magnetic fields oriented along different crystallographic directions are calculated theoretically. It is demonstrated that, in strong magnetic fields, the magnetocaloric effect and the Faraday effect are characterized by strong anisotropy, which disappears in weak magnetic fields. 相似文献
6.
U. V. Valiev J. B. Gruber D. K. Sardar B. Zandi I. S. Kachur A. K. Mukhammadiev V. G. Piryatinskaya V. Yu. Sokolov I. S. Edelman 《Physics of the Solid State》2007,49(1):91-98
The Zeeman effect in the 7 F 6 → 5 D 4 absorption band of the Tb3+ ion in the paramagnetic garnets Tb3Ga5O12 and Tb3Al5O12 was studied. The field dependences of the Zeeman splitting of some absorption lines are found to exhibit unusual behavior: as the magnetic field increases, the band splitting decreases rather than increases. Symmetry analysis relates these lines to 4f → 4f electron transitions of the doublet-quasi-doublet or quasi-doublet-doublet type, for which the field dependences of the splitting differ radically from the well-known field dependences of the Zeeman splitting for quasi-doublet-quasi-doublet or quasi-doublet-singlet transitions in a longitudinal magnetic field. 相似文献
7.
M. S. Aleksanyan V. M. Arakelyan V. M. Aroutiounian A. Z. Adamyan G. E. Shahnazaryan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2010,45(6):291-296
Nanosize films of In2O3:Ga2O3 (96:4 weight %) have been deposited on a glassceramic substrate by the method of rf magnetron sputtering. The surfaces of
fabricated films were studied with use of a scanning electron microscope; sizes of grains were determined and the thicknesses
of films were measured. In order to prepare a gas-sensitive structure, a thin catalytic palladium layer and ohmic comb contacts
were deposited on the In2O3:Ga2O3 film surface by the method of ion-plasma sputtering. The sensitivity of sensors based on the glassceramic/In2O3:Ga2O3 (96:4 weight %)/Pd structure to different concentrations of propane and butane gas mixture, as well as to methane was investigated
at temperatures of working substance from 250 to 300°C. 相似文献
8.
The Young’s moduli along the [100] and [110] crystallographic directions and the shear modulus along the [100] direction in a high-purity yttrium garnet ferrite single crystal are measured in the temperature range from 20 to 600°C. All the independent elastic constants are calculated for this temperature range. The behavior of the elastic moduli and elastic anisotropy factor is analyzed in the vicinity of the critical temperature of the magnetic phase transition. 相似文献
9.
β-Ga2O3 nanowires have been synthesized using Ga metal and H2O vapor at 800 °C in the presence of Ni catalyst on the substrate. Remarkable reduction of the diameter and increase of the
length of the Ga2O3 nanowires are achieved by separation of Ga metal and H2O vapor before they reach the substrate. Transmission electron microscopy analyses indicate that the β-Ga2O3 nanowires possess a single-crystalline structure. Photoluminescence measurements show two broad emission bands centered at
290 nm and 390 nm at room temperature.
Received: 27 June 2002 / Accepted: 7 October 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: +886-6/234-4496, E-mail: wujj@mail.ncku.edu.tw 相似文献
10.
Yu. Zorenko V. Gorbenko T. Voznyak T. Zorenko B. Kuklinski R. Turos-Matysyak M. Grinberg 《Optics and Spectroscopy》2009,106(3):365-374
The processes of excitation energy transfer in phosphors based on single-crystal Tb3Al5O12:Ce (TbAG:Ce) and Tb3Al5O12:Ce,Eu (TbAG:Ce,Eu) garnet films have been investigated. These films are considered to be promising materials for screens for X-ray images and luminescence converters of blue LED radiation. The conditions for excitation energy transfer from the matrix (Tb3+ cations) to Ce3+ and Eu3+ ions in TbAG:Ce and TbAG:Ce,Eu phosphors have been analyzed in detail. It is established that a cascade process of excitation energy transfer from Tb3+ ions to Ce3+ and Eu3+ ions and from Ce3+ ions to Eu3+ ions is implemented in TbAG:Ce,Eu via dipole-dipole interaction and through the Tb3+ cation sublattice. 相似文献
11.
H.W. Kim 《Applied Physics A: Materials Science & Processing》2007,86(3):315-319
We have investigated the effect of growth temperature on structural morphology and photoluminescence (PL) properties of as-synthesized
gallium oxide (Ga2O3) nanostructures. The products consisted of Ga2O3 nanobelts and nanosheets (i.e. wider nanobelts), which had monoclinic crystalline structures. The average width of structures
grown at 1000 °C was relatively greater than those at 800 °C, revealing that higher temperature favored the formation of nanosheets.
PL measurements of 800 °C- and 1000 °C-grown samples indicated that both samples exhibited a broad emission band peaked around
the blue-light region, while only the 800 °C-grown sample showed a red peak.
PACS 81.07.-b; 81.05.Je; 61.10.Nz; 68.37.Hk; 68.37.Lp 相似文献
12.
E. V. Shevchenko E. V. Charnaya E. N. Khazanov A. V. Taranov A. S. Bugaev 《Physics of the Solid State》2017,59(4):733-736
The temperature dependence of the ac magnetic susceptibility of a single-crystal mixed rare-earth garnet Er2HoAl5O12 has been investigated within the range from 1.8 to 300 K in a zero constant field and in applied bias fields of up to 9 T. In the absence of a constant magnetic field the magnetic susceptibility followed the Curie–Weiss law. The application of a constant magnetic field caused a magnetic phase transition, the temperature of which increased with increasing magnetic field. The temperature of the maximum of the ac magnetic susceptibility, which is a characteristic of the phase transition, did not show a noticeable dependence on the frequency of the alternating magnetic field. 相似文献
13.
V. N. Kolobanov V. V. Mikhailin N. N. Petrovnin D. A. Spasskii Yu. V. Zorenko 《Moscow University Physics Bulletin》2007,62(1):34-36
The luminescence spectra of single-crystal films and bulk crystals of yttrium-aluminum garnet Y3Al5O12 and Ce3+-activated Y3Al5O12 were investigated. It was shown that the room-temperature luminescence intensity of the Ce3+-free single-crystal Y3Al5O12 film was considerably lower than that of the bulk crystals, while the luminescence intensity of the Ce3+ ions in the Y3Al5O12:Ce films was considerably higher than that one for the corresponding bulk crystal. 相似文献
14.
A new member of the family of garnets with fast lithium ion conduction has been found with the composition Li7La3Hf2O12. The anion arrangement corresponds to the oxygen framework in garnets, e.g., in Ca3Fe2Si3O12. Hafnium is coordinated octahedrally while the lanthanum environment can be described as a distorted cube. Lithium occupies
a large number of positions with tetrahedral, trigonal planar, and metaprismatic coordination. Li7La3Hf2O12 shows a lithium bulk ion conductivity of 2.4 × 10−4 Ω−1 cm−1 at room temperature with an activation energy of 0.29 eV. 相似文献
15.
The Ca12Al14O33: Yb3+/Yb2+ single phase nano-phosphor has been synthesized through combustion route and its luminescence and lifetime studies have been
carried out up to 20 K using 976 and 266 nm excitations. The samples heated in open atmosphere have shown the presence of
Yb in Yb3+ and Yb2+ states. The 976 nm excitation results a cooperative upconversion emission at 486 nm due to the Yb3+ state and a broad band in the blue region and has been assigned to arise from the defect centers. The 266 nm excitation on
the other hand results a broad emission band even from as-synthesized phosphor without doping of Yb, the width of which increases
in presence of Yb due to the emission from Yb2+ ions formed in heated samples. The white emission covers almost whole visible region with bandwidth 190 nm. The ions in Yb2+ state has been found to increase with the increase in heating temperature up to 1,273 K. A back conversion of Yb2+ to Yb3+ has been observed for higher temperatures. Effect of boric and phosphoric acids as flux on the emission properties of Yb3+ and Yb2+ states have been examined and discussed. Quantum yield of emission has also been determined for different samples. 相似文献
16.
D. H. Zhou X. D. Xu D. Y. Shen D. Z. Li J. Q. Di C. T. Xia F. Wu J. Xu 《Laser Physics》2011,21(11):1876-1879
Optical properties of Ho3+-doped Lu3Al5O12 and (Lu,Y)3Al5O12 crystals were investigated and compared. Substitution of Y for Lu in the host garnet Lu3Al5O12 results in broad absorption and emission spectra, and improvements in the laser behavior of Ho3+. Pumped by Tm:fiber laser, a maximum output power of 5.02 and 5.73 W of Ho-doped Lu3Al5O12 and (Lu,Y)3Al5O12 have been obtained, respectively. The center lasing wavelength are 2124.5 and 2123.0 nm for Lu3Al5O12 and (Lu,Y)3Al5O12, respectively. 相似文献
17.
S. R. Boidedaev 《Russian Physics Journal》2010,53(1):67-70
Experimental investigations of the field dependence of the linear magnetic birefringence (LMB) in an α-Fe2O3:Ga single crystal are presented. It is established that during crystal magnetization in the basal plane near directions perpendicular
to the С2 axes in the region of magnetic field saturation, the LMB changes nonmonotonically. The observed special feature of the field
LMB dependence is due to the reorganization of the magnetic α-Fe2O3:Ga structure during magnetization. 相似文献
18.
19.
O. Volkova E. Goodilin A. Vasiliev D. Khomskii N. Tristan P. Kerschl Yu. Skourski K. -H. Mueller B. Buechner 《JETP Letters》2005,82(10):642-645
The ferrimagnetic compounds Ca(CuxMn3?x)Mn4O12 of the double distorted perovskites AC3B4O12 family exhibit a rapid increase of the ferromagnetic component in magnetization at partial substitution of square coordinated (Mn3+)C for (Cu2+)C. In the transport properties, this is seen as a change of the semiconducting type of resistivity for the metallic one. The evolution of magnetic properties of Ca(CuxMn3?x)Mn4O12 is driven by strong antiferromagnetic exchange interaction of (Cu2+)C with (Mn3+/Mn4+)B coordinated octahedra. The competing interactions of (Mn3+)C with (Mn3+/Mn4+)B lead to the formation of noncollinear magnetic structures that can be aligned by magnetic fields. 相似文献
20.
The dynamics of magnetoelectric RMn2O5 crystals (R=Eu and Gd) was studied in the frequency and temperature ranges 20–300 GHz and 5–50 K, respectively. The crystals possessed magnetic and ferroelectric long-range order and had close transition temperatures, TN, C?36 and 30 K for R=Eu and Gd, respectively. Mixed magneto-lattice excitations were observed in GdMn2O5; the excitations were most intense near the transition temperature T?30 K at frequencies close to the antiferromagnetic resonance frequencies of the Mn subsystem. Along with the antiferromagnetic resonance of the Mn subsystem, the ferromagnetic resonance of the Gd subsystem was observed in GdMn2O5 in an external magnetic field. No such dynamics was characteristic of EuMn2O5. 相似文献