The magnetic properties of the Zr2FeV3O11 vanadate, characterized by a disordered distribution of diamagnetic Zn 2+ and high-spin Fe3+ ions, are studied using magnetization and electron paramagnetic resonance (EPR) measurements. The dc susceptibility reveals antiferromagnetic interactions between Fe3 +spins with a Curie-Weiss temperature Θ = -58(1) K, followed by a transition to a frozen, spin-glass-like state at low temperature T f ≈ 2.55 K, indicating an inhomogeneous magnetic ground state. The temperature variation of the EPR parameters confirms the antiferromagnetic coupling of Fe3+ spins at high temperatures, while a distinct divergence is observed at T ≈ 55 K. This behavior is attributed to the inherent magnetic inhomogeneity of the system due to antiferromagnetic spin clusters.

The magnetic properties of three mononuclear copper complexes where the metal ion is coordinated by Schiff base ligands have been investigated by magnetic susceptibility and electron paramagnetic resonance (EPR) studies. Significant extended magnetic coupling has been observed comprising competing antiferromagnetic and ferromagnetic components, which are explained in terms of the interactions between copper ions mediated through the organic ligands. Distant substitutions in the ligand structure are suggested to affect critically the magnetic coupling leading to frustration effects on the cooperative transition that may develop under favorable structural conditions. The temperature dependence of intensity of the EPR line was studied in the temperature range 130-280K and fitted to the Curie-Weiss-type law. The consistency of magnetic and EPR results is discussed for the three investigated complexes. © 2003 Elsevier B.V. All rights reserved.

The diamagnetic susceptibility of multiwall carbon nanotubes is studied as function of magnetic field and temperature. Both the low-field and the low-temperature susceptibility reveal a definite paramagnetic upturn in qualitative agreement with the Aharonov-Bohm effect. Analysis of the high-field magnetic susceptibility in terms of the orbital diamagnetism of quasi-two-dimensional graphite implies hole-doping and supports further the intrinsically divergent paramagnetic contribution of small metallic nanotubes. © 2003 Elsevier B.V. All rights reserved.

The magnetic properties of the polymerized phase of RbC60 have been investigated by static magnetization measurements. The magnetic susceptibility comprises a temperature dependent part that decreases rapidly below 50 K, where the metal-insulator transition and the subsequent antiferromagnetic ordering are expected according to electron spin resonance results. The temperature variation of this contribution resembles that of quasi-one-dimensional gapped systems and shows substantial field dependence suggesting a disordered antiferromagnetic phase.

The magnetic properties of two series of trivalent rare earth (R 3+) molecular complexes with hydrazone ligands (R=Ce, Pr, Dy, Ho, Er), adopting different crystal structures, have been investigated by static susceptibility measurements. At high temperatures, the magnetic response is dominated by the paramagnetic contribution of R3+ ions determined by the crystal-field interaction. At low temperatures (T<4K), an antiferromagnetic deviation is observed, most pronounced for the series with the heavier R3+ ions. © 2004 Elsevier B.V. All rights reserved.