Quantum matter in high magnetic fields

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Millimetre-wave response of the novel organic superconductors beta ''-ET4[(H3O)M(C2O4)(3)]center dot S (M=Fe3+, S=C6H5CN and C6H5NO2)

SYNTHETIC MET 137:1-3 (2003) 1225-1226

Authors:

A Narduzzo, A Ardavan, AI Coldea, J Singleton, A Akutsu-Sato, H Akutsu, SS Turner, R Day

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.
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Millimetre-wave response of the novel organic superconductors β″-ET4[(H3O)M(C2O4)3 ].S (M=Fe3+, S= C6H5CN and C6H5NO2)

Synthetic Metals 137:1-3 (2003) 1225-1226

Authors:

A Narduzzo, A Ardavan, AI Coldea, J Singleton, A Akutsu-Sato, H Akutsu, SS Turner, P Day

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.
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A mu SR study of the spin dynamics in Ir-diluted layered manganites

PHYSICA B 326:1-4 (2003) 513-517

Authors:

CA Steer, SJ Blundell, AI Coldea, IM Marshall, T Lancaster, PD Battle, D Gallon, AJ Fargus, MJ Rosseinsky

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.
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Changes of the spin dynamics in perovskite and bilayer manganite

PHYSICA B 326:1-4 (2003) 500-504

Authors:

AI Coldea, SJ Blundell, CA Steer, FL Pratt, D Prabhakaran, JF Mitchell

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.
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Spin freezing and magnetic inhomogeneities in bilayer manganites

(2003)

Authors:

AI Coldea, SJ Blundell, CA Steer, JF Mitchell, FL Pratt
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