Amalia Coldea

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.

Abstract:

We report a series of muSR measurements performed on single crystals of La1-x,SrxMnO3, (0 less than or equal to x less than or equal to 0.125) and on a polycrystalline bilayer manganite La2-2x Sr1+2xMn2O7 (v = 0.52). We find that the temperature dependence of the spinlattice relaxation rate is strongl, dependent on the hole doping and the associated changes in the magnetic structure. Y The systems have competing, anisotropic interactions, leading to a complex interplay of charge, spin and orbital order. This has a significant influence on the spin dynamics, both for perovskite and layered manganites. (C) 2002 Elsevier Science B.V. All rights reserved.