Use of electromagnetically induced transparency for measurement of superhyperfine splitting of the levels of rare-earth metals doped in optical crystals

The results of experimental and theoretical investigations of the electromagnetically induced transparency regime on the ⁴ I _9/2-⁴ G _5/2 transition in Nd³⁺ ions doped in LaF₃ are presented. The superhyperfine splitting of the upper and lower working levels has been determined on the basis of the results obtained. A theoretical model adequately describing the parameters of the resonances of electromagnetically induced transparency has been developed by analyzing the experimental data.     

Effect of the polarization of counterpropagating light waves on nonlinear resonances of the electromagnetically induced transparency and absorption in the Hanle configuration

A polarization method has been proposed for transforming the nonlinear electromagnetically induced transparency resonance into the electromagnetically induced absorption resonance (and vice versa) in the Hanle configuration in the field of counterpropagating waves. Numerical calculations have been performed for the F _g = 2 → F _e = 1 and F _g = 2 → F _e = 3 transitions in the ⁸⁷Rb atom. The qualitative analysis of the effect has been performed for the three-level Λ scheme of the atomic energy levels. The main theoretical conclusions are in qualitative agreement with our experimental data for ⁸⁷Rb. The results can be applied in magnetometry and nonlinear optics.     

Observation of spontaneous spin reorientation in Nd1 ? xDyxFe3(BO3)4 ferroborates with a competitive R-Fe exchange

The magnetic, magnetoelectric, and magnetoelastic properties of DyFe₃(BO₃)₄ single crystals and the Nd_0.75Dy_0.25Fe₃(BO₃)₄ substituted compound with the competitive Nd-Fe and Dy-Fe exchange interactions have been investigated in magnetic fields up to 210 kOe. It has been shown that the antiferromagnetic state in Nd_0.75Dy_0.25Fe₃(BO₃)₄ below the Néel temperature is easy-plane and a spontaneous spin-reorientation transition to a uniaxial state occurs near 25 K. Anomalies are observed in various physical characteristics in a spin-flop transition induced by the magnetic field along the trigonal axis. The H-T phase diagrams are constructed; they are in good agreement with a simple model taking into account the anisotropy of the exchange splitting and g factors of the ground doublets of the Dy³⁺ and Nd³⁺ ions. The features of the magnetoelectric effect in various magnetic phases have been studied. Spontaneous electric polarization has been revealed in the region of the existence of an easy-plane antiferromagnetic state in the substituted compound. A qualitative theoretical justification of the possibility of the appearance of the spontaneous spin-reorientation transition in the Nd_0.75Dy_0.25Fe₃(BO₃)₄ substituted compound is given. Original Russian Text ? Yu.F. Popov, A.M. Kadomtseva, G.P. Vorob’ev, A.A. Mukhin, V.Yu. Ivanov, A.M. Kuz’menko, A.S. Prokhorov, L.N. Bezmaternykh, V.L. Temerov, 2009, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 89, No. 7, pp. 405–411.     

Effective regime of electromagnetically induced transparency in a Pr<Superscript>3+</Superscript>:LaF<Subscript>3</Subscript> crystal

The results of experimental and numerical investigations of electromagnetically induced transparency in a Pr³⁺:LaF₃ crystal have been presented. A spectrally isolated Λ system has been made of a specially prepared medium of an ensemble of particles with an inhomogeneous width less than the hyperfine splitting of both upper and lower operating levels. A considerable increase in the transmittance with respect to an unprepared medium has been demonstrated. It has been shown that, under the experimental conditions, the transmittance is limited by the apparatus (spread of the transmission peak by the instrumental linewidth specified by the probe pulse length).     

Electromagnetically induced transparency on Zeeman sublevels in Nd<Superscript>3+</Superscript>:LaF<Subscript>3</Subscript> crystals

The results of experimental observation of the electromagnetically induced transparency regime on the ⁴ I _9/2-⁴ G _5/2 transition in Nd³⁺ ions doping in LaF₃ are presented. The depth and width of the transparency are analyzed as functions of the control field intensity.     

Giant dielectric susceptibility and magnetocapacitance effect in manganites at room temperature

Extremely high values of the relative permittivity up to 10⁷ and the magnetocapacitance up to 10⁵% have been found in La_{1 − x} Sr _x MnO₃ single crystals (x = 0.1, 0.11). These phenomena are observed even at room temperature. The observed behavior can be a consequence of the strong interaction among charge, spin, and lattice degrees of freedom, which leads to charge and phase separation in the regime before the percolation threshold. Original Russian Text ? R.F. Mamin, T. Egami, Z. Marton, C.A. Migachev, M.F. Sadykov, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 10, pp. 731–735.     

Optical study of the electronic structure and magnetic ordering in a weak ferromagnet FeBO3

Spectral dependences of the relative permittivity ɛ = ɛ₁ − iɛ₂ of a uniaxial weak ferromagnet FeBO₃ are measured for two principal polarizations in the energy range 0.6–5.6 eV. The positions have been determined for the charge-transfer transitions that make the main contribution to absorption above the bandgap and determine the refractive-index dispersion below the bandgap. The isotropic magnetic contribution to the refractive index has been detected by studying the temperature dependence of the refractive index in the range 100–700 K; its value (≈2 × 10⁻²) is found to be record high for magnetic dielectrics. The energy shift of the effective oscillator, which characterizes the shift of the positions of the charge-transfer transitions due to magnetic ordering, is determined from these data within the framework of a single-oscillator model. The value of the exchange striction in FeBO₃ is determined from optical measurements. Original Russian Text ? P.A. Markovin, A.M. Kalashnikova, R.V. Pisarev, Th. Rasing, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 822–827.     

Multiplicity fluctuations of particles produced in interactions of light nuclei with carbon nuclei at a momentum of 4.2 A GeV/ c and their theoretical interpretation

New experimental data on fluctuations in the multiplicities of negatively charged particles in interactions of light nuclei (p, d, ⁴He, ¹²C) with carbon nuclei at a momentum of 4.2 A GeV/c in 4π geometry are reported. The data indicate a behavior similar to that earlier observed by the NA49 Collaboration. The cascade evaporation model, FRITIOF model, and UrQMD 1.3 model are used to analyze the data. The dependence of the fluctuations on nuclear collision centrality is theoretically described without any exotic assumptions. According to the FRITIOF model, the dependence of the multiplicity fluctuations on the collision centrality is to a large extent governed by fluctuations in the number of “wounded” nucleons that are associated with the experimental observation conditions. The NA49 Collaboration data are also described. Original Russian Text ? A.S. Galoyan, E.N. Kladnitskaya, V.V. Uzhinsky, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 10, pp. 718–721.     

Observation of electromagnetically induced transparency in cesium molecules

We have studied electromagnetically induced transparency (EIT) in diatomic cesium molecules in a vapor cell by using tunable diode lasers. We have observed a sub-natural Λ-resonance in absorption molecular band B ¹Π _u − X ¹Σ _g ⁺ at different cesium vapor pressures. The width of the EIT resonance shows a linear dependence on a cesium vapor pressure.     

Resonances in the pump-probe spectroscopy of Λ system in alkali atoms

We investigate resonances in the pump-probe spectroscopy of Λ configuration of levels in the hyperfine manifold of D ₂ transition of ¹³³Cs and ^a7Rb with specific reference to Autler-Townes splitting, dressed state resonances in double Λ system and electromagnetically induced transparency. As an application, a dark resonance based magnetometer is briefly discussed.     

Inversion of the relative probabilities of the f-f and f-d transitions in the Ln3+ lanthanide ions at their radio- and sonoexcitation as compared to photoexcitation

The results of measuring the efficiencies of the formation of electronically excited states of the Ln³⁺ lanthanide ions in aqueous solutions in the processes of radioluminescence and multibubble sonoluminescence are analyzed. In both cases, electronic excitation occurs due to inelastic collisions of Ln³⁺ ions with (for radioluminescence) charged ionizing particles in liquid and (for multibubble sonoluminescence) high-energy particles, primarily electrons, in the gas phase of cavitation bubbles. In both processes, the efficiencies of exciting ions whose luminescence states appear in the 4f-5d transitions (Ce³⁺ and Pr³⁺) are significantly lower (by an order of magnitude or larger) than the efficiencies of exciting ions whose luminescence states appear in the 4f-4f transitions (Gd³⁺ and Tb³⁺). Therefore, the probability of the f-d transitions is lower than the probability of the f-f transitions in lanthanide ions excited by collisions with the charged particles and the relative probabilities of these transitions are inverted in these processes as compared to photoexcitation. Original Russian Text ? G.L. Sharipov, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 85, No. 9, pp. 559–562.     

Monoclinic superstructure V14O6 of the tetragonal solid solution of oxygen in vanadium

The monoclinic (space group C2/m) superstructure of V₁₄O₆, which is formed in the atom-vacancy ordering of the tetragonal solid solution of oxygen in vanadium, is studied by the methods of x-ray diffraction and symmetry analysis. It has been found that the channel of the order-disorder phase transition attributed to the formation of the monoclinic suboxide V₁₄O₆ includes six superstructure vectors belonging to three non-Lifshitz stars {k ₁₋₁}, {k ₁₋₂}, and {k _1–3} of one type {k ₁}. The distribution function of the O atoms in the V₁₄O₆ monoclinic superstructure has been calculated. It has been shown that the displacements of V atoms distort the body-centered tetragonal metal sublattice, thus preparing the formation of the fcc sublattice and the transition from the suboxide V₁₄O₆ to the cubic vanadium monoxide with the B1 structure. Original Russian Text ? A.I. Gusev, D.A. Davydov, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 10, pp. 746–751.     

Temperature sensitivity and noise of an HTSC Josephson detector on a sapphire bicrystal substrate at 77 K

In YBa₂Cu₃O_{7 − x} films grown on sapphire bicrystal substrates, the Josephson junctions are prepared based on artificial grain boundaries formed by the turn of the crystal lattices about the [100] axis. The films are deposited by the laser ablation method on the buffer CeO₂ layer. The critical film temperature reaches 88.5 K with a transition width of 1.5 K. Junctions from 2 to 3-μ m wide are integrated into the planar log-periodic antennas and their characteristics are measured at 77 K. The characteristic voltage I _c R _n reaches 570 μV. With exposure to external radiation at a frequency of 113 GHz, the Shapiro steps were observed on the current-voltage characteristic. The temperature sensitivity of this detector placed in a quasi-optical receiving unit is measured. At the modulation of the input radiation temperature 77 K/300 K, a response of more than 200 nV is observed at the detector output. At the modulation frequency, intrinsic noise is about 1 nV/Hz^1/2, which corresponds to a temperature resolution of 1 K. Original Russian Text ? M. Tarasov, E. Stepantsov, A. Kalabukhov, M. Kupriyanov, D. Winkler, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 828–831.     

Er$lt;sup$gt;3+$lt;/sup$gt;：YAlO$lt;sub$gt;3$lt;/sub$gt;晶体中Λ型四能级系统的量子相干左手性

用相干量子干涉和电磁感应透明（Electromagnetically induced transparency,EIT） 效应在Er³⁺：YAlO₃晶体中计算得到了Thommen,Mandel和Kastel对原子气提出的Λ型四能级系统的负折射率.计算结果得到的负折射率对应的频带宽度约为1 MHz,比先前报道的10³ Hz量级要宽得多.通常而言对应于折射/吸收比|Re［n］/lm［n］|≈1,而计算所得结果是|Re［n］/lm［n］|为4.6,表明吸收被EIT效应很好地抑制.Im［n］出现的负值可能与Er³⁺的⁴I_13/2→⁴I_15/2跃迁的受激发射有关.由此可知,稀土离子掺杂材料具有丰富的能级和各种不同的电磁跃迁,也是电磁感应负折射率材料中出色的应用材料的候选者. 关键词： 稀土掺杂晶体 量子干涉 电磁感应透明 负折射率材料     

Charge ordering in crystals of Pr1? x Sr x MnO3 ( x = 0.22, 0.24) ferromagnetic manganites

The structural and magnetic states of Pr_1−x Sr _x MnO₃ (x = 0.22, 0.24) manganite crystals were studied over a wide temperature range. Measurements of the magnetic susceptibility and electrical resistivity demonstrated that these manganites belong to the class of ferromagnetic semiconductors. Thermal neutron elastic scattering patterns revealed that, in the temperature range 4.2–350 K, the manganites have an orthorhombic structure (space group Pnma) with a well-pronounced cooperative Jahn-Teller effect. Major emphasis was placed on the nuclear magnetic superstructure with a wave vector q = (2π/2a, 0, 2π/2c). It was shown that this superstructure suggests 1/4-type charge ordering in the manganites under investigation. Original Russian Text ? S.F. Dubinin, S.G. Teploukhov, V.E. Arkhipov, V.D. Parkhomenko, é.A. Neĭfel’d, A.V. Korolev, N.A. Ugryumova, Ya.M. Mukovskiĭ, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 4, pp. 704–710.     

外加磁场对简并二能级原子系统相干特性的影响

在铯原子简并二能级系统中6S_1/2F=4—6P_3/2 F'=5 的循环跃迁上获得了电磁感应吸收(EIA)峰，并研究了轴向均匀磁场对二能级系统相干效应的影响，即存在轴向均匀磁场时，观测到在铯原子6S_1/2F=4—6P_3/2F'=5 跃迁频率处EIA和电磁诱导透明(EIT)的混合结构，在合适的实验条件下，其结果与Ye等(2002)的理论分析相一致. 关键词： 电磁感应吸收(EIA) 铯原子 简并二能级系统     

Effect of high pressure and chemical substitution on the crystal structure and magnetic state of R2Fe17 ? x Six (R = Lu or Y; x = 0 or 1.7)

The effect of high pressure on the crystal structure of the intermetallic compounds R₂Fe_{17 − x} Si_x (R = Lu or Y; x = 0 or 1.7) was studied using neutron diffraction. A correlation between changes in structural parameters and magnetic properties under the action of high pressure, as well as under chemical substitution of Si for Fe atoms, was analyzed in terms of localized moment and spin fluctuation models. The spin fluctuation model was found to describe more adequately the experimentally observed increase in the Curie temperature upon chemical substitution and the decrease in this temperature under the action of high pressure. Possible reasons for the suppression of a collinear ferromagnetic state and the occurrence of a noncollinear antiferromagnetic state in R₂Fe_17−x Si_x under pressure are discussed based on estimated differences between the total energy minima of these states. Original Russian Text ? D.P. Kozlenko, V.I. Voronin, V.P. Glazkov, B.N. Savenko, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 675–680.     

Anomalous hall effect in HoB12

Within a wide temperature range of 1.8–300 K, the Hall effect in holmium dodecaboride is investigated. The measurements of the angular dependences of the Hall resistance ρ_H(φ, T, H) for HoB₁₂ performed in a high magnetic field up to 80 kOe at helium and intermediate temperatures made it possible to separate the normal and anomalous contributions to the Hall effect. Analysis of the anomalous component behavior in the paramagnetic and Néel phases suggests the appearance of the 5d-state magnetic polarization (the spin polaron effect) and makes it possible to compare the revealed features of the Hall coefficient R _H(T, H) with the H-T magnetic phase diagram of HoB₁₂. Original Russian Text ? N.E. Sluchanko, D.N. Sluchanko, V.V. Glushkov, S.V. Demishev, N.A. Samarin, N.Yu. Shitsevalova, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 691–694.     

Cross sections and other parameters ofe − − H2O scattering (E i⩾50 eV)

Our previous theoretical work one ⁻ − H₂O scattering has been modified and extended to intermediate and high energiesE _i. Using the Bethe plot, we compare the present inelastic cross-sections with the experimental ionization cross sections. Total cross-sections are analytically represented asQ _TOT(cm²)=a.(E _ieV) ^−b and the parameters ‘a’ and ‘b’ are discussed for molecules H₂O, NH₃ and CH₄ in the rangeE _i=100–1000eV.