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Static magnetometry and continuous-wave and pulsed-electron spin resonance (ESR) is used for the characterization of the neutral radical cluster [Al(Al ₃R ₃) ₂] ^• (R=N(SiMe ₂Ph) ₂). For temperatures below 25 K, we prove its monoradical character, a g-factor of 1.997–1.991, and a three time larger hyperfine interaction with the central than with the six outer ²⁷Al nuclei of the [Al ₇R ₆] ^• cluster radical. Temperature dependence of the low-temperature spin-lattice relaxation is analysed. At temperatures above 30 K, the effective moment per cluster increases, and the hyperfine interaction with the seven ²⁷Al nuclei is equalized.

Tailoring magnetic interactions of organic solids is currently an area of intense research activity. We show that the quasi-one dimensional anti-ferromagnetic exchange coupling of the well-known organic free radical triphenylverdazyl (TPV) can be increased by a factor of 3 by systematic molecular modifications (i.e. J _1d/ k _B = −16K for 1,3,5,6-tetraphenyl-verdazyl). 1,3,5-tri-6'-(1,3,5-triphenylverdazyl)-benzene as a representative of covalently bound multiradical molecules was analyzed as solid and in solution. The energetic spin-doublet-quartet separation and intermolecular exchange interaction were estimated. Cooperative magnetic behaviour with ordering temperature of about 40K and well-defined hysteresis loops ( H _c(5 K) ≈ 40 Oe) has been achieved by the chelation of transition metals (e.g. Mn) in appropriate organic materials. NMR, ESR, static magnetic susceptibility, in part also a.c. susceptibility, specific heat and x-ray...

For the quasi–one-dimensional conductor (fluoranthene) ₂PF ₆, the anisotropy of the quasi-microscopic restriction to free diffusive motion of the charge and spin carriers is analyzed by static magnetic field gradient spin echo electron spin resonance.

Since electron spin resonance (ESR) is a sensitive tool for the characterisation of microstructures of pyrolytic carbon, we applied spatially resolved ESR for detecting the homogeneity of the gas phase reactions required for chemical vapour deposition and to monitor resulting pyrolytic carbon coatings in a non-destructive way. The filtered back-projection variant of continuous-wave ESR imaging was used to achieve three-dimensional images of the ESR signal intensity with a voxel size of (60 μm) ³.

Conduction electron spin echo attenuation in well defined magnetic field gradients provides more accurate values of the anisotropy of electron spin motion than microwave conductivity measurements. The electron spin diffusion coefficient for motion along the perylene (PE) radical cation stack, , in the PE hexafluoroarsenate salt is influenced temperature dependently by perpendicular-to-stack motion and reflects the varying average unrestricted chain length, . The anisotropy of is larger than 7300:1 at 250 K.

The specific heat of the quasi-one-dimensional organic conductor pyrene hexafluoroarsenate ((Py) ₇(Py) ₄(AsF ₆) ₄·4CH ₂Cl ₂) was measured between 10 and 250 K using the method of continuous heating. The contribution of the lattice to the specific heat was modelled using the Debye model and Einstein terms. The variation of the specific heat at the structural phase transition that is accompanied by 60° rotation of one of the stacked pyrene molecules could be reproduced well using a cooperation model including the formation of domains, and the surprisingly high transition entropy was explained qualitatively.

The low-temperature proton spin–lattice relaxation is analysed for lanthanum hydrides LaH _x intentionally doped with Gd or Ce. These paramagnetic impurities were also characterized by static magnetic susceptibility and electron spin resonance measurements. A quantitative description of the proton relaxation rate maxima, as well as of the electron spin relaxation data, is presented. These analyses indicate that the density of states at the rare earth site disappears only for .

For (pyrene) ₁₂(SbF ₆) ₇ a 10 ⁴:1 anisotropy of the microwave conductivity is observed. We show that the timescale for the end of the one-dimensional motion of the conduction electron spins derived by analysis of the frequency and temperature dependence of the proton spin–lattice relaxation and of the electron spin resonance linewidth and relaxation times is governed to a comparable degree by perpendicular-to-stack hopping and by interaction with intrastack paramagnetic localized defects in these crystals. The electron spin self-diffusion coefficient derived for the magnetic field gradient parallel to the pyrene stacking direction is therefore influenced by perpendicular-to-stack motion as well.

The electron spin resonance line-width anisotropy and intensity are analysed for the quasi-one-dimensional organic conductors (fluoranthene) ₂PF ₆ and (perylene) ₂PF ₆·2/3 tetrahydrofurane in the metallic phase above the Peierls transition temperature. Based on the bottleneck model of relaxation, the temperature dependence of the intra-stack exchange constant between conduction-electron spins and localized defect spins is derived and discussed.

Nuclear magnetic resonance of ²D nuclei is measured in the paramagnetic phase of TbMn ₂D ₂ powder samples. Static and dynamic contributions of Mn and Tb moments to the nuclear probes are characterized on approach to the ordering temperature T _N = 272 K and the possibility of antiferromagnetic correlations between Mn and Tb magnetic moments is analysed. Field and temperature dependence of the magnetization in the ordered state is presented as well.