Quantum matter in high magnetic fields

Abstract:

Transport measurements have been carried out on single crystals of the charge transfer salt beta"-(BEDT-TTF)(4)[(H3O) Ga3+ (C2O4)(3)]. C6H5NO2, using magnetic fields of up to 33 T and temperatures down to 0.55 K. The material is found to be superconducting with T. 7.5 K and an in-plane critical field B-c2 greater than or equal to 33 T, and to exhibit Shubnikov-de Haas (SdH) oscillations. The temperature and angle dependence of the Shubnikov-de Haas oscillations and the upper critical field are reported, allowing information about the anisotropy of the upper critical field, effective mass m*, and the Fermi-surface (FS) of the material to be deduced.

Abstract:

Transport measurements have been carried out on single crystals of the charge transfer salt β″-(BEDT-TTF)4[(H3O)Ga³⁺(C2 O4)3]. C6H5NO2, using magnetic fields of up to 33 T and temperatures down to 0.55 K. The material is found to be superconducting with Tc ≈ 7.5 K and an in-plane critical field Bc2 ≥ 33 T, and to exhibit Shubnikov-de Haas (SdH) oscillations. The temperature and angle dependence of the Shubnikov-de Haas oscillations and the upper critical field are reported, allowing information about the anisotropy of the upper critical field, effective mass m*, and the Fermi-surface (FS) of the material to be deduced.

Abstract:

The high frequency (f=70 GHz) magneto-optical response of beta"-ET4[(H3O)M(C2O4)(3)].S, where M=Fe3+, S=C6H5CN and C6H5NO2, has been investigated in the temperature range 1.4 K < T < 120 K. The angle dependence of the EPR spectra and the anisotropy of the g-factors for the two materials are presented.

Abstract:

The millimeter-wave response of the novel organic superconductors was studied. The magneto-optical response of the two samples containing Fe³⁺ ions and the host solvents benzonitrile and nitrobenzene. The angle dependence of the electron paramagnetic resonance (EPR) spectra and the anisotropy of the g-factors for the two materials were presented. The angle of dependence of the absorption spectra at 1.4 K for the two samples were compared.

Abstract:

Dilution on the B-site with Ir or Rh can lead to the enhancement of ferromagnetic couplings in layered manganites. We report a muSR study of the spin dynamics of the layered manganites La0.25Sr1.75MnpIr1-pO4 (p = 0.5, 0.75) as a function of the dilution. We have characterized the static magnetic behavior using SQUID magnetic measurements and used muon spin relaxation spectroscopy to provide evidence for short-range ferromagnetic correlations. Furthermore, the effect of dilution on the critical dynamics in this two-dimensional spin system is reported and related to the dynamics above and below the critical percolation threshold. (C) 2002 Elsevier Science B.V. All rights reserved.