Mapping the B,T phase diagram of frustrated metamagnet CuFeO2

The magnetic phase diagram of CuFeO2 as a function of applied magnetic field and temperature is thoroughly explored and expanded, both for magnetic fields applied parallel and perpendicular to the material's c-axis. Pulsed field magnetization measurements extend the typical magnetic staircase of CuFeO2 at various temperatures, demonstrating the persistence of the recently discovered high field metamagnetic transition up to Tn2 ~ 11 K in both field configurations. An extension of the previously introduced phenomenological spin model used to describe the high field magnetization process (Phys. Rev. B, 80, 012406 (2009)) is applied to each of the consecutive low-field commensurate spin structures, yielding a semi-quantitative simulation and intuitive description of the entire experimental magnetization process in both relevant field directions with a single set of parameters.Comment: 14 pages, 11 figures, submitted to Phys. Rev.

High-field recovery of the undistorted triangular lattice in the frustrated metamagnet CuFeO2

Pulsed field magnetization experiments extend the typical metamagnetic staircase of CuFeO2 up to 58 T to reveal an additional first order phase transition at high field for both the parallel and perpendicular field configuration. Virtually complete isotropic behavior is retrieved only above this transition, indicating the high-field recovery of the undistorted triangular lattice. A consistent phenomenological rationalization for the field dependence and metamagnetism crossover of the system is provided, demonstrating the importance of both spin-phonon coupling and a small field-dependent easy-axis anisotropy in accurately describing the magnetization process of CuFeO2.Comment: 4 pages, 4 figure

Phonon and crystal field excitations in geometrically frustrated rare earth titanates

The phonon and crystal field excitations in several rare earth titanate pyrochlores are investigated. Magnetic measurements on single crystals of Gd2Ti2O7, Tb2Ti2O7, Dy2Ti2O7 and Ho2Ti2O7 are used for characterization, while Raman spectroscopy and terahertz time domain spectroscopy are employed to probe the excitations of the materials. The lattice excitations are found to be analogous across the compounds over the whole temperature range investigated (295-4 K). The resulting full phononic characterization of the R2Ti2O7 pyrochlore structure is then used to identify crystal field excitations observed in the materials. Several crystal field excitations have been observed in Tb2Ti2O7 in Raman spectroscopy for the first time, among which all of the previously reported excitations. The presence of additional crystal field excitations, however, suggests the presence of two inequivalent Tb3+ sites in the low temperature structure. Furthermore, the crystal field level at approximately 13 cm-1 is found to be both Raman and dipole active, indicating broken inversion symmetry in the system and thus undermining its current symmetry interpretation. In addition, evidence is found for a significant crystal field-phonon coupling in Tb2Ti2O7. These findings call for a careful reassessment of the low temperature structure of Tb2Ti2O7, which may serve to improve its theoretical understanding.Comment: 13 pages, 7 figure

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores

The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R 2T i2O 7 (R = Sm, Eu, Gd, Tb,Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk susceptibilities of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed. © 2010 IOP Publishing Ltd

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores

The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R 2T i2O 7 (R = Sm, Eu, Gd, Tb,Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk susceptibilities of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed. © 2010 IOP Publishing Ltd

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores

The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R 2T i2O 7 (R = Sm, Eu, Gd, Tb,Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk susceptibilities of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed. © 2010 IOP Publishing Ltd

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores

The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R 2T i2O 7 (R = Sm, Eu, Gd, Tb,Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk susceptibilities of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed. © 2010 IOP Publishing Ltd

Acute liver failure secondary to metastatic liver infiltration: Case report and review of the literature

We present the case of a patient who died from multiple organ failure due to acute liver failure as a result of malignant hepatic infiltration by an adenocarcinoma. A review of the literature revealed that the clinical picture, laboratory examination, and imaging studies do not contribute to the diagnosis of this rare cause of liver failure. Therefore, liver biopsy should be considered early in the process, as this diagnosis is a contraindication for orthotopic liver transplantation

High-field recovery of the undistorted triangular lattice in the frustrated metamagnet CuFeO2.

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