Collapse of a region of the magnetic phase diagram of elemental terbium under a strain-induced Lifshitz transition

AC susceptibility and neutron scattering measurements are used to study the magnetic field-temperature magnetic phase diagram of a Tb single crystal under uniaxial tension along its hexagonal c axis. An external magnetic field is applied in the basal plane. We focus on the region in the phase diagram that corresponds to the helical antiferromagnetic phase and find that this region collapses when the uniaxial tension is increased beyond a critical value as low as 600 bar. There are strong reasons to associate this collapse with an underlying Lifshitz transition in the Fermi surface of Tb's valence electrons. We use a finite-temperature ab initio theory to analyze our measurements, obtaining a pressure-temperature magnetic phase diagram in very good agreement with experiment. Our calculations indicate that short- and long-range magnetic order has a crucial effect on the Fermi surface nesting and consequent magnetism of Tb

Systematics of c-axis Phonons in the Thallium and Bismuth Based Cuprate Superconductors

We present grazing incidence reflectivity measurements in the far infrared region at temperatures above and below Tc for a series of thallium (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi(2-x)Pb(x)Sr2CaCu2O8) based cuprate superconductors. From the spectra, which are dominated by the c-axis phonons, longitudinal frequencies (LO) are directly obtained. The reflectivity curves are well fitted by a series of Lorentz oscillators. In this way the transverse (TO) phonon frequencies were accurately determined. On the basis of the comparative study of the Bi and Tl based cuprates with different number of CuO2 layers per unit cell, we suggest modifications of the assignment of the main oxygen modes. We compare the LO frequencies in Bi2Sr2CaCu2O8 and Tl2Ba2Ca2Cu3O10 obtained from intrinsic Josephson junction characteristics with our measurements, and explain the discrepancy in LO frequencies obtained by the two different methods.Comment: 8 pages Revtex, 6 eps figures, 3 tables, to appear in Phys. Rev.

Collapse of a region of the magnetic phase diagram of elemental terbium under a strain-induced Lifshitz transition

AC susceptibility and neutron scattering measurements are used to study the magnetic field-temperature magnetic phase diagram of a Tb single crystal under uniaxial tension along its hexagonal c axis. An external magnetic field is applied in the basal plane. We focus on the region in the phase diagram that corresponds to the helical antiferromagnetic phase and find that this region collapses when the uniaxial tension is increased beyond a critical value as low as 600 bar. There are strong reasons to associate this collapse with an underlying Lifshitz transition in the Fermi surface of Tb's valence electrons. We use a finite-temperature ab initio theory to analyze our measurements, obtaining a pressure-temperature magnetic phase diagram in very good agreement with experiment. Our calculations indicate that short- and long-range magnetic order has a crucial effect on the Fermi surface nesting and consequent magnetism of Tb

Magnetic and structural properties of Sc(Fe1−xSix)2 Laves phases studied by Mössbauer spectroscopy and neutron diffraction

The investigations of iron-containing phases existing in fly ashes were performed using transmission Mössbauer spectrometry. The examined samples of fly ashes were collected from different coal combustion systems, that is, stoker-fired boiler in municipal heating plant and pulverized coal boiler in power plant. Several phases are identifi ed in the samples: iron oxides, paramagnetic aluminosilicate glass with Fe3+ ions and Al2O4- -type spinel with Fe2+ ions. It was pointed out that proportions of contents of phases strongly depend not only on the combustion temperature but also on the way of ash collection

Magnetic Structures of the LiNi0.9Co0.1PO4 Crystal

We present the magnetic structures and properties of single crystal and polycrystalline samples LiNi0.9Co0.1PO4 obtained by conventional self f lux LiCl growth from solution and glycerol nitrate methods, respectively. The samples were studied with magnetic property measurement system, X ray and neutron diffraction. A symmetry analysis of possible magnetic structures for the propagation vectors kC 0 and kIC 0, k, 0 was carried out. The magnetic structures in the LiNi0.9Co0.1PO4 single crystal are commensurate kC 0 and incommensurate kIC 0, k, 0 antiferromagnetic orders. The module k is equal 0.10 0.12 reciprocal lattice units at low temperatures. At 7 K, the magnetic moment of the 3d ion is 2.0 amp; 956;B and decreases to zero at 21 K. The temperatures of magnetic phase transitions determined during magnetic property measurements are similar in single crystal and polycrystalline samples. Single crystal neutron diffraction is made it possible to observe some details of the incommensurate structur

Magnetic and structural properties of Sc(Fe1−xSix)2 Laves phases studied by Mössbauer spectroscopy and neutron diffraction

The investigations of iron-containing phases existing in fly ashes were performed using transmission Mössbauer spectrometry. The examined samples of fly ashes were collected from different coal combustion systems, that is, stoker-fired boiler in municipal heating plant and pulverized coal boiler in power plant. Several phases are identifi ed in the samples: iron oxides, paramagnetic aluminosilicate glass with Fe3+ ions and Al2O4- -type spinel with Fe2+ ions. It was pointed out that proportions of contents of phases strongly depend not only on the combustion temperature but also on the way of ash collection

Neutron studies of cation disorder in Zn2FeV3O 11-δ

Polycrystalline Zn2FeV3O11-δ samples were studied by neutron diffraction and ac magnetic susceptibility in the temperature range of 10-300K. This material, crystallizing in the triclinic space group P1, has a complicated structure with cation disorder. Down to 10K, no magnetic long-range order was found, in contrast to suggestions based on the temperature dependence of the static magnetic susceptibility and electron paramagnetic resonance (EPR). Essential differences in the positions of the metal ions were observed relative to those calculated earlier from X-ray diffraction (XRD). It is proposed that disorder of iron and zinc atoms could be responsible for significant differences in the physical properties reported for this compound. © 2004 Elsevier B.V. All rights reserved