A review of some of the solid state and the magnetic properties of fullerenes is presented. We summarise and discuss experimental results on magnetism of pure C60, C70 and higher fullerenes. The main features of the structure and the magnetic properties of intercalated fullerenes, such as metallofullerenes, TDAE-C60 and polymeric A1C60, are presented. Attention is also paid to the mixed state properties of fullerene superconductors, especially to the evaluation of the critical fields and the characteristic lengths of these materials. Some new experimental results on this subject are also presented.

We report on detailed magnetic investigations of big K 3 C 60 single crystals with sizes of ϳ1 mm. The samples were characterized by x-ray analysis, neutron diffraction, and ac magnetization measurements. The temperature dependence of the upper and lower critical fields was obtained, the latter by the trapped magneticmoment method. The coherence length and the penetration depth at Tϭ0 and close to the transition temperature were evaluated. The magnetic field and the temperature dependence of the critical current density were studied and the irreversibility lines determined. Long-term magnetic relaxation, measured in a wide range of temperatures and magnetic fields, allowed us to obtain the temperature dependence of the relaxation rate and the flux creep activation energy at different magnetic fields. The influence of sample inhomogeneities on all these properties was investigated. The results are compared to those obtained on powder and polycrystalline samples.

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The influence of fast neutron irradiation on flux pinning in HgBa 2 Ca 2 Cu 3 O 8ϩx single crystals (T c ϭ120 K) subjected to a fluence of 5ϫ10 17 cm Ϫ2 was studied. Magnetic measurements were performed using a commercial superconducting quantum interference device magnetometer and a miniaturized torque magnetometer. In the unirradiated state, the irreversibility line ͑IL͒, plotted as ln(H irr ) vs ln(1ϪT irr /T c ), shows two slopes. At higher temperatures ͑85-100 K͒ the IL is described by a power-law dependence H irr (T)ϭH irr (0) (1ϪT irr /T c ) ␣ with ␣Ϸ2.1. At lower temperatures ͑25-60 K͒, a more rapid change of H irr with temperature is observed, with the exponent ␣Ϸ4.8. Irradiation shifts the IL to significantly higher magnetic fields/ temperatures, where it is rather well described by a single power-law dependence with the exponent ␣Ϸ2.3. The effective mass anisotropy ␥ϭ(m c /m ab ) 1/2 , as determined from torque measurements, decreases after neutron irradiation. The shielding current density as a function of temperature up to 60 K is well approximated by the exponential dependence j s (T)ϭ j s (0)exp(ϪT/T 0 ). Irradiation increases the characteristic temperature T 0 from about 5.9 K ͑in the as-prepared crystal͒ to T 0 ϭ9.4 K, clearly reflecting a slower decay of j s with temperature. Neutron-generated defects significantly increase j s and suppress the ''fishtail effect'' ͑an increase of j s with magnetic field͒, which was present for the unirradiated crystal.

Magnetic, magnetocaloric and transport properties of alloys of system Ni-Mn-In has been investigated. Large magnetocaloric effect have been observed at temperatures below room, making it a potential material system for various applications.

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