Correlation of fluctuation field and temperature coefficient of coercivity in a CoCrPtB thin film

The effect of the ratio of fluctuation field (H_f) to coercivity (H_c) on the temperature coefficient of coercivity [α(H_c)] was investigated for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr, Co₆₉Cr₁₉Pt₉Ta₃/Cr, and Co₈₆Cr₁₀Ta₄/Cr thin films (longitudinal recording media) with very small average grain volume (V_phy). α(H_c) increases markedly with increase in temperature between near 250 and 350 K for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr thin films. α(H_c) is approximately proportional to the ratio H_f/H_c for all thin films, as in the case of advanced data backup tapes prepared from ultrafine particles. α(H_c) and the ratio H_f/H_c increase as V_phy decreases. Smaller H_f/H_c values are necessary for small α(H_c) values, which is very important for the thermal stability of high-density recording media with very small V_phy.     

Proximity effect in the finite and incommensurate ferromagnet/superconductor systems

The original theory of a proximity effect is proposed for the bi- and tri-layered system ferromagnetic metal/superconductor (F/S) in dirty limit. The F₁/S/F₂ trilayer is examined more closely. The distinctions in materials, in thicknesses of F layers (d_f1 and d_f2), in parameters interfaces, and in local environments of layers are considered among the causes of incommensurability of trilayer. The peculiar T_c(d_f1, d_f2) interference pattern is predicted for the F₁/S/F₂ systems. The reentrant superconductivity and possibility of the better observability of the spin-valve regime are discussed.     

Effect of conduction band nonprabolicity on the Rashba spin splitting of AlGaN/GaN QWs

By using the perturbation expansion method and self-consistent iterative method, we evaluate the effect of the conduction band nonprabolicity on the wave vector (k_t) dependent Rashba coefficient (α) and nonlinear Rashba spin splitting (ΔE) in the Al_0.5Ga_0.5N/GaN quantum well (QW). The effective mass (energy) under the first order approximation m_t1 (E_k1) is in proximity to the iterative result m_tp (E_kp) and m_t1>m_tp, E_k1<E_kp, showing the higher order contributions to m_t (E_k) are small. The sign of the nonparabolic correction to E_k is just opposite to that of the correction to m_t. The increase of α and ΔE due to the conduction band nonparabolicity reaches about 3% at k_t=1 nm⁻¹. Around the left heterointerface, the probability density is high and E_k0>E_kp>E_k1, so α₀<α_p<α₁, ΔE₀<ΔE_p<ΔE₁. With increasing k_t, α decreases, and ΔE increases slowly. For small k_t, α₀ (ΔE₀), α₁ (ΔE₁) and α_p (ΔE_p) are nearly the same. While for large k_t, the difference between α₀ and α₁ (α_p) increases rapidly, but the difference between ΔE₀ and ΔE₁ (ΔE_p) increases slowly.     

Infrared spectra of 1-phosphapropyne,CH3CP,and its perdeuteride,CD3CP

The infrared spectra of 1-phosphapropyne, CH₃CP, and its perdeuteride, CD₃CP, have been measured in the gaseous and solid states. The Q_K branches of perpendicular bands have been analyzed in terms of the usual quadratic expression in K. Fermi resonances were identified for the ν₁, ν₂ + ν₃, 2ν₃, 2ν₆⁰; and ν₅, 2ν₃ + ν₈ band systems of CH₃CP and the ν₁, 2ν₃, 2ν₆⁰; ν₆, ν₇ + ν₈; and ν₇, 3ν₈¹ band systems of CD₃CP. The xy Coriolis interaction was also identified between the ν₃ and ν₆ bands of the two species. All the fundamentals were assigned and the normal coordinate treatment was carried out along with the Coriolis constants, ζ^z.     

The perturbative approach to the critical behaviour of two-matrix models in the limit N → ∞

We construct representations of the Heisenberg algebra by pushing the perturbation expansion to high orders. If the multiplication operators B_1,2 tend to differential operators of order l_2,1, respectively, the singularity is characterized by (l₁, l₂). Let l₁ ⩾ l₂. Then the two cases, (A) “l₂ does not divide l₁” and (B) “l₂ divides l₁”, need a different treatment. The universality classes are labelled [p, q] where [p, q] = [l₁,l₂] in case (A) and [p, q]=[l₁ + 1,l₂] in case (B).     

Quantitative T(1)(ρ) imaging using phase cycling for B0 and B1 field inhomogeneity compensation

T_1ρ imaging is useful in a number of clinical applications. T_1ρ preparation methods, however, are sensitive to non-uniformities of the B₀ magnetic field and the B₁ RF field. These common system imperfections can result in image artifacts and quantification errors in T_1ρ imaging. We report on a phase-cycling method which can eliminate B₁ RF inhomogeneity effects in T_1ρ imaging. This method does not only correct for image artifacts but also for T_2ρ contamination caused by B₁ RF inhomogeneity. The presence of B₀ magnetic field inhomogeneity can compromise the effectiveness of this method for B₁ RF inhomogeneity correction. We demonstrate that, by combining the spin-locking scheme reported by Dixon et al. (Myocardial suppression in vivo by spin locking with composite pulses. Magn Reson Med 1996; 36:90-94) with phase cycling, we can simultaneously correct B₀ magnetic field inhomogeneity effects and B₁ RF inhomogeneity effects in T_1ρ imaging. Phantom and in vivo data sets are used to demonstrate the proposed methods and to compare them with other existing T_1ρ preparation methods.     

High-resolution Fourier spectroscopy of 14N2 and 15N2 infrared emission spectrum: Analysis of the B′3Σu−-B3Πg system

The rotational analysis of some bands of the B′³Σ_u^?-B³Π_g system of nitrogen (¹⁴N₂ and ¹⁵N₂) excited in a microwave discharge and recorded under high resolution with a Fourier transform interferometer allowed the determination of molecular constants for the v = 0, 1, 2 levels in the B′³Σ_u^? state. Main equilibrium constants of the B′³Σ_u^? state for ¹⁴N₂ and ¹⁵N₂ are (in cm^?1) T_e = 5789.2178 (relative to B³Π_g (v = 0); ω_e = 1516.6239; ω_ex_e = 11.9721; B_e = 1.473 098; α_B = 0.01 664; ω_eⁱ = 1465.3549; ω_ex_eⁱ = 11.1783; B_eⁱ = 1.375 209; α_Bⁱ = 0.01 505.     

Nonisotropic L-conversion-electron — X-ray directional correlations in160Dy

The directional correlations betweenL-conversion electrons andL x-rays have been measured. The electrons were emitted in the 86.78keV 2⁺→0⁺ transition in¹⁶⁰Dy, in the decay of¹⁶⁰Tb. The experimental results areA ₂₂(e _L -x _Li )=0.085 (22),A ₂₂(e _L -x _Lα )=0.0066 (29),A ₂₂(e _L -x _Lβ )=0.0000 (27), andA ₂₂(e _L -x _Lγ )=0.0096 78). These results are in disagreement with published theoretical values. It is suggested that the discrepancy is due to a phase inconsistency in the internal conversion matrix elements and there is good agreement withA ₂₂ values calculated in this work.     

A sequence of two ferrotoroidal phase transitions in nickel-bromine boracite Ni3B7O13Br

The phenomenological theory of a sequence of two second-order phase transitions in Ni-Br boracite is presented. Two different components of the toroidal moment vector T _i are the order parameters of these transitions. Expressions are derived for the temperature dependences of the spontaneous values of T _i , polarization P _i , and magnetization M _i and the dielectric χ_ij=dP _i /dE _j , magnetic k _ij =dM _i /H _j , and magnetoelectric α _ij=dP _i /dH _j =dM _j /dE _i susceptibilities. Some of these susceptibilities display sharp temperature peaks in the vicinity of phase transitions.     

Polarization properties of Li2−x Na x Ge4O9 (0.2 ≤ x ≤ 0.3) crystals

The polarization switching in sinusoidal fields and the pyroelectric properties of Li_2?x Na _x Ge₄O₉ (0.2 ≤ x ≤ 0.3) crystals are measured in the temperature range T _c ?T ≤ 40 K. The behavior of the P?E hysteresis loops with variations in temperature is investigated for crystals with phase transition temperatures T _c < 300 K and T _c > 300 K. It is shown that, for crystals with phase transition temperatures T _c < 300 K, the temperature dependence of the hysteresis loop exhibits a behavior typical of crystals with second-order phase transitions. The crystals with phase transition temperatures T _c > 300 K are characterized by double hysteresis loops in the temperature range T _c ?T ₁ ≈ 30 K. The correlation between the polarization properties and possible structural transformations of the Li_2?x Na _x Ge₄O₉ crystals due to the change in the concentration ratio of Na and Li ions is discussed.     

Microwave spectrum of monodeuterated diacetylene due to vibrationally induced dipole moment

Microwave spectrum of monodeuterated diacetylene (HCCCCD), which is nonpolar in the equilibrium configuration, was observed in various excited states of bending vibrations. Dipole moments in the ν₆, 2ν₆, and ν₆ + ν₉ vibrational states were determined from the Stark effect measurement to be 0.0907(6), 0.1681(14), and 0.0900(4) D with uncertainties in parentheses, where ν₆ and ν₉ denote respectively the CCH bending and lowest frequency bending vibrations. The l-type doubling constant in the ν₆ state is 2.1316(28) MHz. Rotational constants were determined in MHz; ν₆(Π), 4086.2165(44); 2ν₆(Δ), 4087.6963(58); ν₆ + ν₉(Δ), 4097.7537(50); 2ν₈(Δ), 4094.4786(103); ν₆ + ν₇(Δ), 4092.9074(176); ν₇ + ν₈(Δ), 4095.8925(354); 2ν₆ + ν₉(Φ), 4098.9505(339).     

The ν7 vibrational states of C3O2: A least-squares fit of the rigid-bender model to the v7ν7l7 energies and rotational constants

The rigid-bender model is used to treat the large-amplitude, low-frequency, bending vibration ν₇ of C₃O₂. Different parameterizations of the bending potential function are considered, and a simple two-term power series is found to give the best fit. With this parameterization, using a least-squares fit to energies and B values, the ν₇ potential function is determined for the ground state as well as for the states in which ν₂, ν₃, ν₄, ν₆, 2ν₆, ν₁ + ν₃, ν₁ + ν₄, ν₂ + ν₃, and 2ν₂ + ν₄ are excited. The excitation of other vibrations has in some cases a drastic effect on the ν₇ potential. In the ground state the potential has a 29 cm^?1 barrier at the linear position, in ν₁ + ν₃ the barrier increases to 79 cm^?1, while in 2ν₂ + ν₄ the barrier vanishes. An equilibrium potential is determined by correcting the ground state potential for the effects of zero-point motion of the normal vibrations ν₁, …, ν₆. This potential has a 35.6-cm^?1 barrier with a minimum at α = 11.14°, where 2α is the angular deviation from linearity. The model accurately predicts the quartic and sextic centrifugal distortion terms for the low-lying v₇ν₇^l₇ states. Second-order l-type coupling is included in the calculations of the quartic terms. The effects of this coupling, which are most pronounced for the ν₇ ≥ 2 states, adequately explain the negative D term recently reported for the ν₂ + 4ν₇⁰ state.     

Measurement of L X-ray fluorescence cross sections and relative intensities for some elements in the atomic range 78 ≤ Z ≤ 92

The L X-ray fluorescence cross sections (σ_Ll, σ_Lα, σ_Lη, σ_Lβ, σ_Lβ6, σ_Lβ2,₄, σ_Lβ1,₃, σ_Lβ9,10, σ_Lγ, σ_Lγ1, σ_Lγ2,3, σ_Lγ4 and σ_Lγ5) and relative intensities (I_Lα, I_Ll, I_Lη, I_Lβ, I_Lβ6, I_Lβ2,4, I_Lβ1,3, I_Lβ9,10, I_Lγ, I_Lγ1, I_Lγ2,3, I_Lγ4 and I_Lγ5) for some elements in the atomic range 78 ≤ Z ≤ 92 have been measured at 59.54 keV photons energies from an Am-241 point source. The L X-rays emitted by samples have been counted by a Si(Li) detector. The L X-ray fluorescence cross sections and relative intensities have been also calculated theoretically by using atomic parameters. The measured values have been compared with the theoretical values.     

Observations of multi-phase microstructures in R2(Fe1−xCox)14B where R=Nd or Dy

Multi-phase microstructures were observed in the psuedo-quaternary phase field of the 2–14–1 magnet materials Nd₂Fe₁₄B, Nd₂Co₁₄B, Dy₂Fe₁₄B, and Dy₂Co₁₄B. At equilibrium, (Nd_1−yDy_y)₂(Fe_1−xCo_x)₁₄B had heretofore been widely assumed to be single phase where 1>x>0 and 1>y>0. In this study, three-phase microstructures were observed in (Nd_1−yDy_y)₂(Fe_1−xCo_x)₁₄B when x>0.3 and y>0.5. The Curie temperatures and peritectic decomposition temperatures for Nd₂(Fe_1−xCo_x)₁₄B are reported for several values of x in the range 1>x>0.     

Decay constants of heavy mesons from a QCD relativistic potential model

We compute masses and leptonic decay constants of charmed and beauty pseudoscalar and vector mesons by using a QCD-inspired relativistic potential model. We obtain results in agreement with the available experimental data; as for the pseudoscalar meson decay constants, we predict f_D=1.38f_π,f_Ds=1.51f_π,f_B=1.75f_π,f_Bs=1.86f _π.     

Laser Stark and laser microwave double-resonance spectroscopy of deuterated fluoroacetylene with the CO2 laser

The CO₂ laser Stark spectrum of deuterated fluoroacetylene was identified with the aid of the double-resonance technique for the ν₃, ν₃ + ν₅ ? ν₅, ν₃ + ν₄ ? ν₄, ν₃ + 2ν₅ ? 2ν₅, and ν₃ + ν₄ + ν₅ ? ν₄ ? ν₅ vibrational bands. Laser microwave double-resonance signals were observed in the presence of the Stark field. From the analysis of the double-resonance signals precise values of the dipole moment were obtained for 10 vibrational states, in Debye, with the uncertainties in parentheses: ground, 0.73292(22); ν₅, 0.75656(17); ν₄, 0.68412(24); 2ν₅(Σ⁺), 0.78063(21); ν₄ + ν₅(Σ⁺ or Σ^?), 0.70698(19); ν₃, 0.75772(30); ν₃ + ν₅, 0.78270(18); ν₃ + ν₄, 0.70822(17); ν₃ + 2ν₅(Σ⁺), 0.80808(25); ν₃ + ν₄ + ν₅(Σ⁺ or Σ^?), 0.73329(17). The band origins were determined (in cm^?1); ν₃, 1045.9242(8); ν₃ + ν₅ ? ν₅, 1049.6441(8); ν₃ + ν₄ ? ν₄, 1047.8700(8); ν₃ + 2ν₅ ? 2ν₅(Σ⁺-Σ⁺), 1053.0374(8); ν₃ + ν₄ + ν₅ ? ν₄ ? ν₅(Σ⁺?Σ⁺ or Σ^??Σ^?), 1051.5040(8).     

First- and second-order Coriolis interactions in symmetric top molecules: Application to the microwave spectrum of cyclopentadienyl thallium

Matrix elements are derived for both first- and second-order Coriolis interactions between A₁ and E₁ vibrational modes in symmetric tops, with particular reference to sign. The results are applied to the observed microwave transitions J → J + 1 for A₁ and E₁ states of the C_5ν molecule cyclopentadienyl thallium in various excited vibrational states. The microwave transitions in the excited A₁ states v₄ = 1, 2, 3, the excited E′ state v′₀ = 1 and the combination state v₄ = 1, v′₀ = 1 have yielded constants which are anomalous in several respects (1). Coriolis interactions between the ν₄ and ν₁₀ vibrations are shown to account for the observed anomalies.     

Ionic conductivity of substituted Li7TaO6 phases

Lithium ion conductivity in solid solutions of Li₇Ta_1-xNb_xO₆, Li₇Ta_1-xBi_xO₆, Li_7+xTa_1-xZr_xO₆ and Li_7-2xCa_xTaO₆ has been measured as a function of temperature and composition using the complex impedance method. At 200°C the conductivities of Li₇Ta_0.7Nb_0.3O₆, Li_7.4Ta_0.6Zr_0.4O₆ and Li_6.6Ca_0.2TaO₆ are 4.3 × 10^-4(ωcm)^-1, 3.0 × 10^-4(ωcm)^-1, 4.0 × 10^-4(ωcm)^-1 and 1.6 × 10^-4(ωcm)^-1 respectively. The results are discussed in relation to structural properties.     

Magnetic properties of (Mn1 − x Fe x )1.68Sn solid solutions

Solid solutions in the (Mn_{1 ? x} Fe _x )_1.68Sn system (x ≤ 0.5) with a Ni₂In-type structure are synthesized by the solid-phase reaction method in a stepwise temperature regime. The unit cell parameters a and c decrease with an increase in the iron concentration in the alloys and become equal to a = 0.430 nm and c = 0.538 nm for the (Mn_0.5Fe_0.5)_1.68Sn alloy. A superstructure with the unit cell parameters a _ss = 3a and c _ss = c is revealed in alloys of the system under investigation. The specific magnetization of the alloys increases nonlinearly from 53 G cm³ g^?1 in the Mn_1.68Sn alloy to 72 G cm³ g^?1 in the (Mn_0.5Fe_0.5)_1.68Sn solid solution. The Curie temperature changes from 270 K in the initial alloy of the composition Mn_1.68Sn to 365 K in the alloy of the composition (Mn_0.5Fe_0.5)_1.68Sn. All solid solutions in the (Mn_{1 ? x} Fe _x )_1.68Sn (x ≤ 0.5) system exhibit metallic conductivity in the temperature range from 77 to 450 K.     

Excitation transfer and quenching induced in inelastic collisions of Zn 41P1 and 43P1 atoms

Quenching of excited Zn(4¹P₁) and Zn(4³P₁) atoms by collisions with Ar, N₂, H₂, CO and CO₂ has been investigated using methods of fluorescence spectroscopy. Mixtures of Zn vapor and quenching gases topped-up with Ar to maintain constant pressure were irradiated in a quartz cell with 2139 or 3076 Å resonance radiation which excited the 4¹P₁ or the 4³P₁ state, respectively. The resulting resonance fluorescence and sensitized fluorescence were monitored in relation to the gas density. Intensity measurements yielded the following cross sections Q_tot for the overall collisional deexcitation of the ¹P₁ state, Q₃ for quenching of the ³P₁ state, and Q₁₃ for ¹P₁→³P_J excitation transfer.For N₂: Q_tot = 26, Q₃ = 4.4, Q₁₃ = 5.8; for H₂: Q_tot = 12, Q₃ = 21, Q₁₃ < 5 × 10^-3; for CO: Q_tot = 28, Q₃ = 14, Q₁₃ = 17; for CO₂: Q_tot = 76, Q₃ = 23. All values are in Ų.