Papers by Roger Macfarlane
Physical Review B, 1988
Raman study of the effect of oxygen stoichiometry on the phonon spectrum of the high-T c supercon... more Raman study of the effect of oxygen stoichiometry on the phonon spectrum of the high-T c superconductor YBa 2 Cu 3 O x. RM Macfarlane, HJ Rosen, EM Engler, RD Jacowitz, and VY Lee IBM Research Division, Almaden Research ...
The narrowest inhomogeneous optical linewidth ever seen in a solid has been observed in Eu(OH)(,3... more The narrowest inhomogeneous optical linewidth ever seen in a solid has been observed in Eu(OH)(,3). This transition is quadratically enhanced in a magnetic field and the results are explained completely in terms of second order perturbation theory and the coupling of crystal field energy levels. Optical coherent transients are reported here for the first time in this optically pure, stoichiometric material. The optical dephasing time, T(,2), is shown to be greater than 2 microseconds for the ('7)F(,0)-('5)D(,0) zero phonon transition. Hole burning, attributed to optical pumping of nuclear-quadrupole levels, has been used to measure the quadrupole splittings in the excited, ('5)D(,0), state. Due to the small magnetic moment, conventional magnetic resonance techniques have failed to make this measurement in all Europium compounds. The new technique developed and used in these hole burning measurements yields the quadrupole coupling coefficients, (VBAR)P(VBAR) = 11.6 MHz...
ECS Meeting Abstracts, 2010
not Available.
Physical Review B, 1970
Using a perturbation expansion based on a strong cubic-Geld zeroth-order approximation, we have o... more Using a perturbation expansion based on a strong cubic-Geld zeroth-order approximation, we have obtained analytical expressions for the g values of the t2', A2, and 'E terms for d' impurity ions in trigonal crystal Gelds. We have compared these expressions whth the results of a numerical calculation in which the magnetic dipole operator was transformed to the basis of eigenvectors of the zero-6eld Hamiltonian computed within the complete d con6guration, and we Gnd them to be a very good approximation. This is not true of the published g-value expressions which are currently available. Absolute magnetic dipole absorption cross sections and nonlinear g values are also calculated. This the Grst time such a detailed calculation of these quantities has been made for transition-ion impurity systems. For levels derived from cubic terms other than tP, 4A 2, and 2E, the analytical-perturbation techniques are not satisfactory and numerical methods must be used. We present an analysis of the g values of the nominally t23 terms, 4A2, 'A, 'T&, and~T&, for emerald, ruby, ZnA1204. Cr'+, MgO:Cr'+, and ZnO:Co'+, and of magnetic dipole absorption cross sections for centrosymmetric ZnA1204.. Cr'+ and MgO:Cr'+. These systems were chosen because there are quite extensive experimental data available on them. The model parameters were determined from the zero-field energy levels, and very good agreement with experiment was obtained in our calculation of the g values and absorption strengths. This provides con6dence in the validity of the crystal-field model to predict the magnetic properties of at least the tP levels, which couple weakly to phonons.
Optics Letters, 1993
Spectral hole burning is reported for the trivalent thulium ion with measurements on the 3 H 6 (1... more Spectral hole burning is reported for the trivalent thulium ion with measurements on the 3 H 6 (1) _ 3 H 4 (1) transition of LaF 3 :Tm3+ and two sites (A and B) of CaF 2 :Tm3+ at 1.5 K. Hole burning occurs by population storage in the metastable 3 F 4 level. The holes were scanned by an electric-field ramp applied directly to the sample, the frequency being calibrated by burning multiple holes with a frequency-modulated laser. This yielded the hole widths as well as the Stark coefficients for the transition studied, which are 8.3 kHz/V cm-' parallel to the C 2 axis (LaF 3 :Tm3+) and for CaF 2 :Tm 3 + are 25 kHz/V cm-' (site A), and 4.6 kHz/V cm-' (site B) for fields along the (001) direction. From the polarization behavior of the holes, the sites in CaF 2 are assigned to the F-compensated C4V and C3, sites, respectively.
Physical Review B, 1988
We report on the effect of rare-earth substitution on the Raman spectra of RBa2Cu307 perovskites ... more We report on the effect of rare-earth substitution on the Raman spectra of RBa2Cu307 perovskites where R Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Tm, and Lu. These spectra show both the presence of Raman modes that are intrinsic to the superconducting material and also those due to impurity phases. The intrinsic Raman modes near 340 cm ' and 500 cm ' which have been attributed, respectively, to Cu(2)-O(2, 3) bending and Cu(1)-O(4) stretching vibrations, show substantial and systematic variations in vibrational frequency as a function of the ionic radius of the rare earth. These variations are in good agreement with neutron-scattering determinations of bond lengths, which supports the vibrational assignment of these modes. PrBa2Cu307 shows no anomalous behavior in its vibrational spectrum even though it was the only sample studied that was not superconducting. This suggests that the valency of Pr is similar to the other rare earths studied and cannot account for the absence of superconductivity in this material. Assignment of other Raman modes in the rare-earth spectra requires identification of impurity phases, which even in small concentrations, can significantly contribute to the Raman spectra. Impurity phases can be preferentially at the surface of samples and can be substantially modified by heat treatment in an argon atmosphere. These impurity phases have previously been confused with disorder-induced Raman modes.
Physical Review Letters, 2014
We show that the coherence properties of the nuclear spin states of rare-earth ions in solids can... more We show that the coherence properties of the nuclear spin states of rare-earth ions in solids can be manipulated by small applied electric fields. This was done by measuring the Stark effect on the nuclear quadrupole transitions of 151 Eu in Y 2 SiO 5 (YSO) using a combination of Raman heterodyne optical detection and Stark modulated quadrupole echoes to achieve high sensitivity. The measured Stark coefficients were 0.42 and 1.0 Hz cm=V for the two quadrupole transitions at 34.54 and 46.20 MHz, respectively. The long decoherence time of the nuclear spin states (25 ms) allowed us to make the measurements in very low electric fields of ∼10 V=cm, which produced 100% modulation of the nuclear spin echo, and to measure Stark shifts of ∼1 Hz or 20 ppm of the inhomogeneous linewidth.
We report the results of Raman measurements performed on polycrystalline samples of superconducti... more We report the results of Raman measurements performed on polycrystalline samples of superconducting TlâCa/sub n/ââBaâCu/sub n/O/sub 4+2//sub n/ (n = 1,2,3) with well-characterized transport, magnetic, and structural properties. The room-temperature first-order Raman spectra of polycrystalline samples of predominantly TlâBaâCuOâ, TlâCaBaâCuâOâ, and TlâCaâBaâCuâOââ phases, with respective superconducting transition temperatures of 10, 110, and 125 K display a systematic variation with the number of CuOâ layers and great similarities with the Raman spectrum of YBaâCuâOâ. Comparison with Raman spectra of the impurity phase candidates BaCOâ, BaOâ, BaCuOâ, CaCuOâ, TlâOâ, and TlCaâCuâO/sub x/ allows identification of intrinsic Raman modes of the superconducting phases. Factor group analysis of the three body-centered tetragonal structures space group 14/mmm, yields the mode classifications and the atoms involved in the modes of Aâ/sub g/ and Bâ/sub g/ symmetry corresponding to c-axis m...
Scandium and Erbium metallofullerenes have been isolated using HPLC techniques and characterized ... more Scandium and Erbium metallofullerenes have been isolated using HPLC techniques and characterized by NMR, optical and far IR spectroscopy. In particular, Sc NMR spectra of Sc_2@C_2n species for several n have been obtained, and far infrared spectra of both discandium and and dierbium metallofullerenes have been measured. These show structure in the 20-200 cm-2 where vibrations of the encapsulated metal atoms are expected. Fluorescence spectra from dierbium metallofullerenes in the 1.5 μm region have been obtained at He and room temperatures.
Curtis's Botanical Magazine, 2000
QWIF pssvvese hsge viliee oger wfrlne ummryF he txonomyD reltionshipsD distriution nd ulturl requ... more QWIF pssvvese hsge viliee oger wfrlne ummryF he txonomyD reltionshipsD distriution nd ulturl requireE ments of the xorth emerin pritillri pudi (urshA prengel (vilieeAD re disussedF en illustrtion is provided nd full desription is givenF
Curtis's Botanical Magazine, 2000
QWSF pssvvese eppsxs viliee oger wfrlne ummryF pritillri ffinis (hultFA ely (vilieeA is one of th... more QWSF pssvvese eppsxs viliee oger wfrlne ummryF pritillri ffinis (hultFA ely (vilieeA is one of the most widespred nd vrile of the western xorth emerin speiesF sts txonomi historyD reltionshipsD distriution nd ulturl requirements re disussedY full desription nd n illustrtion re providedF
Physical Review B, 1989
Absorption spectra of Tm'+: Y3A1,0» are reported between 1.9 and 0.26 pm at 15 and 90 K, and betw... more Absorption spectra of Tm'+: Y3A1,0» are reported between 1.9 and 0.26 pm at 15 and 90 K, and between 0.80 and 0.35 pm at 1.6 K. Laser-excited emission obtained at 80 K is also reported from the Tm'+ manifolds 'D2, 'G&, H4, and F4 to the ground-state manifold, 'H6. The emission from 'D2 also includes transitions to Stark levels in manifolds F4, F3, and F2. Analysis of the emission spectra confirms the experimental crystal-field splitting deduced from an analysis of the hot-band absorption data. Both emission and absorption spectra indicate that Tm'+ ions occupy several diff'erent sites although the majority of Tm'+ ions appear to substitute for Y'+ ions in dodecahedral lattice sites (D2 point-group symmetry). The most intense spectra are analyzed assuming selection rules for D2 symmetry. A lattice-sum calculation predicts a symmetry of I 2 for the ground state. Using this result the symmetries of 20 I" l 11 I 2 17 I 3 and 18 I 4 Stark levels were identified experimentally and compared with results from a crystal-field splitting calculation. A Hamiltonian consisting of Coulombic, spin-orbit, interconfiguration-interaction, and crystal-field (D& symmetry) terms was parametrized and diagonalized for all manifolds of the Tm' (4f ') configuration. The rms deviation between 66 experimental and calculated Stark levels was 11 cm 12
The dephasing time T2 (gammah= 1/piT2 is the homogeneous linewidth) of the ^4I15/2 -- ^4I13/2 tra... more The dephasing time T2 (gammah= 1/piT2 is the homogeneous linewidth) of the ^4I15/2 -- ^4I13/2 transition of Er^3+ in a silicate optical fiber was measured by two-pulse photon echoes vs. external magnetic field and temperature. A field of 2 T reduces the homogeneous linewidth by 1.8 MHz from its value of 3.2 MHz at zero field, an anomalously large reduction compared to that in oxide crystals with similar Er^3+ concentration. We propose that the dephasing is caused by two classes of low frequency tunneling modes: elastic ``two-level-systems'' (TLS) responsible for 1.4 MHz and coupled spin-elastic TLS modes for 1.8 MHz. The coupled modes acquire a magnetic character from an elastic Er^3+ spin-TLS interaction. The temperature dependence of the homogeneous linewidth is linear in the measured range of 1.4 to 4 K. Three- pulse photon echo decays measured from 0.5 mus to 500 mus and at a field of 5 T characterized spectral diffusion caused by the distribution of TLS tunneling rate...
Solid State Communications, 1989
ABSTRACT We report Raman microprobe spectra taken from a single Tl2Ca2Ba2Cu3O10 crystal on a supe... more ABSTRACT We report Raman microprobe spectra taken from a single Tl2Ca2Ba2Cu3O10 crystal on a superconducting film (Tc = 120K) with the phase identify confirmed by electron microprobe analysis and x-ray diffraction. The CuO bond bending mode of B1g symmetry is identified with the peak at 237 cm−1. All other modes are found to have A1g symmetry.
Science, 1996
Page 1. Th~ree-Color, -Sate, ree-ensional Ds pla ... Thec de-ViCe fett.~iresunco111Ciinhe,red vie... more Page 1. Th~ree-Color, -Sate, ree-ensional Ds pla ... Thec de-ViCe fett.~iresunco111Ciinhe,red viewing" acce'ss to mul,1tipleA uIsers, siiiiul,tan1eOUSIVs' an1d is. ca-_ p"ible of dispLaing,Inf,irmal11.tion USIng the threec ~iddit ve priiiiIrv color's red, g,reen, and1o bI tie (FPig. ...
Physics Letters A, 1978
ABSTRACT
Uploads
Papers by Roger Macfarlane