Costas Dimitropoulos

  • Citations Per Year
Learn More
55Mn NMR line shape measurements in La1-xCaxMnO3 for 0.20< or =x< or =0.50 provide experimental evidence about the existence of two distinct regions in the T-x magnetic phase diagram, where the homogeneous ferromagnetic (FM) metallic state is separated into FM metallic and FM insulating regions. These results are in agreement with recent theoretical(More)
55Mn and 139La NMR measurements on a high quality single crystal of ferromagnetic (FM) La0.80Ca0.20MnO3 demonstrate the formation of localized Mn(3+,4+) states below 70 K, accompanied by a strong cooling-rate dependent increase of certain FM neutron Bragg peaks. (55,139)(1/T(1)) spin-lattice and (139)(1/T(2)) spin-spin relaxation rates are strongly enhanced(More)
Recent and novel data obtained from chlorine NQR measurements on natural and deuterated (NH 4 )2 MC16 compounds are discussed with special regard to the influence of the ammonium-ion dynamics on the structural stability of these crystals. The temperature dependence (4.2 K to 350 K) of the chlorine NOR frequency \ q and relaxation rates Tj-1 , T2 1 obtained(More)
We report (139)La nuclear magnetic resonance in ferromagnetic and insulating (FMI) La(1-x)Ca(x)MnO(3), 0.10< or =x< or =0.20, which at low temperatures shows the formation of Mn octants with enhanced Mn-O wave function overlapping and electron-spin alignment. The rapid increase of the relaxation rates and the "wipeout" of the (139)La NMR signal intensity on(More)
The temperature and isotope dependence of the 3 5 , 3 7 C1-NQR spin-lattice relaxation rate near the cubic to tr igonal phase transit ion at TCl = 87 K has been investigated in both (NH 4 ) 2 TeCl 6 and (ND 4 ) 2 TeCl 6 salts. In the temperature range of ~ 2 0 K above and ~ 10 K below TCl, the relaxation obeys the relation (Tj • T) cc(T—TCl). This behaviour(More)
The 35C1 NQ R frequency and spin-lattice relaxation rate in the compounds A2PbCl6 (A = C s, Rb, NH4, K) have been investigated in the range 4.2 K to 500 K, and as a function o f pressure at room temperature. NQR experiments conducted on (K: NH 4)2PbCl6 mixed crystals have been used to complete the NQR-frequency versus temperature diagram o f K2PbCl6,(More)
l13Cd NMR measurements in two Ag-Cd samples cycled between room temperature and temperatures below M, are presented. The growth curve of the martensite on cooling presents a discontinuity in the cycling temperature region. It is shown that the method of analysis of the NMR data recently developed by us [Phys.Rev.B 46, 10563 (1992)], allows to detect subtle(More)
By using nuclear magnetic resonance techniques we show that for T<30 K the La0.875Sr0.125MnO3 compound displays a nonuniform charge distribution, comprised of two interconnected Mn ion subsystems with different spin, orbital, and charge couplings. The NMR results agree very well with the two spin wave stiffness constants observed at small q values in the(More)
  • 1