J. Phys. IV France 114 (2004) 347
Electron spin resonance studies of the organic superconductor -(BEDT-TTF) 4[ (H 3O)Fe(C 2O 4) 3] C 6H 5CNA. Narduzzo1, A. Ardavan1, J. Singleton2, L. Pardi3, V. Bercu3, A. Akutsu-Sato4, 1, H. Akutsu4, 1, S.S. Turner4 and P. Day4
1 The Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK firstname.lastname@example.org
2 National High Magnetic Field Laboratory, Los Alamos National Laboratory, TA-35, Los Alamos, USA
3 Istituto per i Processi Chimico-Fisici, CNR, Via Moruzzi 1, 56124 Pisa, Italy
4 Davy-Faraday Research Laboratory, The Royal Institution, 21 Albemarle Street, London W1X 4BS, UK
We applied magneto-optical techniques to investigate the electron spin resonance (ESR) spectra of single crystal and powder samples of the organic superconductor -(BEDT- TTF) 4[ (H 3O)Fe (C 2O 4) 3] C 6H 5CN. Data were obtained in magnetic fields up to 10 Tesla using both cylindrical and rectangular resonators at 55, 63 and 72 GHz and transmission measurements at 95 and 190 GHz with field modulation. Analysis of the high field-high frequency ESR lines for different field orientations and temperatures allows the determination of the g-value anisotropy and the zero-field splitting parameters for the Fe 3+ ions ( S=5/2), showing that they occupy a site with distorted octahedral symmetry. The temperature and frequency dependences of the magneto-optical spectra are used to identify the nature of the interaction between localised Fe spins and between the local moments and the delocalised carriers. Key words. Electron Spin Resonance. Antiferromagnetism. Type-II superconductor. Vortex state.
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