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1.
Electron spin resonance studies have been carried out on Cu2+ ion doped in single crystals of cadmium maleate dihydrate at 303 and 77K. It has been found that Cu2+ enters this lattice interstitially. The spin Hamiltonian parameters have been evaluated and the ground state wave function
is found to be predominantly |X
2 −Y
2〉 with a slight admixture of |3Z
2 −r
2〉. 相似文献
2.
3.
《Journal of magnetism and magnetic materials》2001,234(2):289-293
The electron spin resonance (ESR) spectra of antiferromagnetic nanoparticle NiO specimens have been investigated as a function of temperature at x-band (microwave) frequencies. Below the nominal Néel temperature, the x-band resonances arising from the bulk antiferromagnets, including NiO particles with diameters greater than 100 Å, all vanish due to the emergence of large molecular exchange fields. The ESR resonance signals of 60 Å antiferromagnetic nanoparticles, however, persist to the lowest temperatures. These nanoparticle resonance lines shift to lower fields rapidly as the temperature is decreased, while the lineshapes broaden and distort. 相似文献
4.
A. S. Aleksandrovsky I. A. Gudim A. S. Krylov V. L. Temerov 《Physics of the Solid State》2007,49(9):1695-1699
The optical absorption and luminescence spectra of single crystals of yttrium aluminum borate YAl3(BO3)4 doped with manganese ions are measured. It is established that the optical absorption spectra of yttrium aluminum borate single crystals doped with manganese ions are determined primarily by the contribution from the Mn4+ ions. The luminescence spectra of the YAl3(BO3)4 single crystals doped with manganese exhibit narrow lines attributed to the Mn4+ ions and an extended multiband structure which is associated primarily with the contribution from the Mn2+ ions. 相似文献
5.
M. D. Hossain 《Applied Physics A: Materials Science & Processing》1982,29(1):29-32
The dielectric properties of titanium doped magnesium oxide (Ti/MgO) and gadolinium doped magnesium oxide (Gd/MgO) single crystals have been measured at room temperature over the frequency range 500 Hz to 50 kHz. For both the crystals, the dielectric constant is found to be independent of frequency and the ac conductivity Re{ae} agrees well with the relation Re{ae}
n
, being the angular frequency with n=0.84±0.05 for Ti/MgO andn=0.81±0.03 for Gd/MgO. The data fits well with the relation
n–1(n<1), being the dielectric loss factor. An explanation may be found on the basis of the hopping phenomenon. 相似文献
6.
Angular distribution measurements of KX reactive scattering of a potassium dimer K2 beam by allyl and alkyl halides are reported. The centre of mass differential cross sections are uncertainly determined but distinctly different from the rebound cross sections exhibited by K+CH3I, C2H5I atom reactions. This change of dynamics may be rationalized in terms of the transfer of both K2 valence electrons to the halide molecule. The reaction products seem likely to be a potassium halide and a potassium alkyl or allyl molecule. 相似文献
7.
ESR signal with hyperfine structure due to Mn and that due to dangling bonds are observed. From the magnitude of the hyperfine structure constant, Mn is considered to locate within voids without making a covalent bond with the host atom in the form of Mn2+. The intensity of the ESR signal due to dangling bonds decreases with the increase of that due to Mn, so it is likely that electrons are transfered from Mn to dangling bonds and their unpaired electrons are paired up. 相似文献
8.
ESR and optical absorption studies have been carried out on Cu2+-doped lithium hydrazinium sulphate single crystals at 303 K. The spin-Hamiltonian parameters evaluated indicate a N2O2 square planar environment for Cu2+ ion in this lattice. The correlation ofESR and crystal structure data leads us to conclude that Cu2+ ion enters the lattice interstitially. Charge compensation is achieved by the release of protons. Using the optical absorption
andESR data, bonding parameters and orbital reduction factors are also evaluated. 相似文献
9.
Five different types of radical pairs produced in single crystals of 1-methyl-uracil by irradiation with X-rays were identified. Partial differentiation between pairs was achieved by utilizing different stabilities versus ultraviolet illumination or annealing, and variation of relative yields with temperature. The composition of pairs was derived from hyperfine couplings, the orientation from the maxima of dipolar couplings. These were found to agree with the directional cosines obtained from the crystal structure. Further evidence was provided by half-field spectra (Δm S=2). The zero-field splitting constant D was determined for five pairs, the value of E for one pair. Second-order effects observed at 9·5 GHz and at 35 GHz have been fully analysed for two pairs by application of the appropriate theory which permitted to determine the absolute sign of D. Two pairs are homogeneously composed of hydrogen abstraction radicals 1-methyleneuracil. These are located two layers apart for one pair with the link normal to the molecular planes (D/gβ = -107·5 G), and within one plane for the other (-224·0 G). The three remaining pairs consist heterogeneously of an abstraction radical and a hydrogen addition radical 1-methyl-5,6-dihydrouracil-6-yl. Two of these are intraplanar (-180·0 G; -129·0 G), and the other one located in neighbouring layers (-183·0 G). 相似文献
10.
Electron spin resonance studies were carried out on VO2+ in cadmium maleate dihydrate single crystals at 303 K. The spin hamiltonian parameters were evaluated. The results lead us
to conclude that like Cu2+, VO2+ enters the lattice interstitially. 相似文献
11.
12.
13.
D. V. Azamat A. G. Badalyan P. G. Baranov P. P. Syrnikov V. A. Trepakov J. Rosa L. Jastrabik 《JETP Letters》1999,69(12):943-948
Copper pair centers, which could be of interest for obtaining quantitative information about exchange interactions in superconductors
based on cuprate perovskites, are observed in crystals with the perovskite structure by the ESR method. Such centers are investigated
in KTaO3:Cu and K1−x
LixTaO3:Cu crystals. A model consisting of a chain of two equivalent Cu2+ ions and three oxygen vacancies, extending along the 〈 100〉 axis, is proposed for the centers. The exchange interaction in
the pairs is ferromagnetic.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 12, 890–894 (25 June 1999) 相似文献
14.
V. A. Vazhenin A. P. Potapov A. D. Gorlov V. A. Chernyshev S. A. Kazanskiĭ A. I. Ryskin 《Physics of the Solid State》2006,48(4):686-692
Trigonal and monoclinic Gd3+ centers with close initial splittings that have no analogs in crystals without yttrium are detected in the electron spin resonance spectrum of Y0.03Cd0.97F2.03: Gd3+ single crystals. The centers observed are attributed to gadolinium ions localized in tetrahedral yttrium and yttrium-cadmium clusters. The values of the parameters of the second-rank spin Hamiltonian are explained (in order of magnitude) in terms of a superposition model that uses the tetrahedral-cluster structure obtained by minimizing the energy of a lattice with a rare-earth cluster. 相似文献
15.
The nature of paramagnetic centres trapped in X-irradiated Na2SO4 single crystals containing chlorine as impurity has been determined from E.S.R. measurements both at room and liquid nitrogen temperatures. ClO3, ClO2, SO4 - and O3 - are the paramagnetic centres identified. The g and A parameters of ClO3 change considerably between 298 K and 77 K. Thus the parameters of ClO3 obtained at 298 K are gxx = 2·0123, gyy = 2·0143, gzz = 2·0206 G and those of the A-tensor are Axx = 97, Ayy = 100 and Azz = 112 G. The parameters obtained for the same centre at 77 K are gxx = 2·0132, gyy = 2·0173, gzz = 2·0073 G and those of the A-tensor are Axx = 130·6, Ayy = 146·3 and Azz = 181·2 G. The temperature variation of the principal values are determined in the temperature range between 298 K and 77 K. These data can be interpreted on the assumption that ClO3 undergoes libration at room temperature, which is frozen out reversibly on cooling. The structure and mechanism of these defects are discussed further. 相似文献
16.
The electron spin resonance (ESR) spectra of undoped and manganese-doped BSCCO (2212) crystals (nominal composition Bi2Sr2CaCu2–x
MnxOy, where x=0.1) are compared.
Zh. Tekh. Fiz. 67, 137–138 (October 1997) 相似文献
17.
The photoinduced optical absorption α of doped yttrium iron garnets (YIG) is investigated. It is found that the optical absorption
α at a wavelength of 1.1 μm depends on the wavelength of irradiating light in the range 0.6–1.9 μm. It is demonstrated that,
in the Y3Fe5O12 crystal with an acceptor Ba impurity, the photoinduced increase in α is due to the formation of Fe4+ ions in octahedral sites. The charge transfer occurs through photoexcitation of the 6
A
1g
(6
S) → 4
T
1g
(4
G) and 6
A
1g
(6
S) → 4
T
2g
(4
G) transitions of octahedral Fe3+ ions. In the crystal with a donor Si impurity, the increase in α is caused by the formation of Fe2+ ions upon photoionization of silicon.
__________
Translated from Fizika Tverdogo Tela, Vol. 43, No. 7, 2001, pp. 1233–1235.
Original Russian Text Copyright ? 2001 by Doroshenko, Nadezhdin. 相似文献
18.
Electron spin resonance has been studied in V1?xCrxO2 crystals in the monoclinic insulating phase M1(x<0.3%). Two distinct substitutional Cr3+ centers are observed. The two centers differ in their axial character which we interpret as due to different charge compensation mechanisms. One of the centers is preponderant at higher Cr concentrations (x>0.1%) and its spectrum can be interpreted by assuming charge compensation by a nearest neighbour V5+. 相似文献
19.
An E.S.R. line-shape model is developed for fast tumbling three-spin systems in nematic liquid crystals. The line positions are calculated from a spin hamiltonian, which considers Zeeman, exchange, dipolar and hyperfine interactions of the three unpaired electrons. The dominant spin relaxation process, determining the line-widths, is assumed to result from the anisotropy of the zero-field splitting coupled to the molecular motion. The predictions of the theory are tested by comparison with the temperature-dependent E.S.R. spectra of trisverdazyl radicals in 4,4′-azoxydianisole. Good agreement is found between experimental and simulated spectra. A detailed analysis provides values for the solute order parameters [Pbar] 2 and [Pbar] 4. They correspond surprisingly well to predictions of the molecular-field theories of nematic liquid crystals. 相似文献