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K0.05MoO2 has been studied by x-ray and neutron diffractometry, electrical resistivity, magnetization, heat capacity, and thermal expansion measurements. The compound displays two phase transitions, a first-order phase transition near room temperature and a second-order transition near 54 K. Below the transition at 54 K, a weak magnetic anomaly is observed and the electrical resistivity is well described by a power-law temperature dependence with exponent near 0.5. The phase transitions in the K-doped MoO2 compound have been discussed for the first time using neutron diffraction, high resolution thermal expansion, and heat capacity measurements as a function of temperature.

CuO nanograins (NGs) and CuO nanowires (NWs) on the top of nanograins samples were produced by the electrical resistive heating method. The NGs sample shows absence of long range magnetic order and strong field-induced ferromagnetic behavior. In the sample comprised of NWs on the top of NGs, a long-ranged antiferromagnetic ordering is induced by a magnetic field of 5 kOe and coexists with an enhanced ferromagnetic-like contribution. The ferromagnetic behavior is observed below and above the temperature-induced TN suggesting that this behavior is not dependent on the original magnetic state of the system, whether it is paramagnetic (PM) or antiferromagnetic.

The effect of weak dipolar interactions (DIs) between Ni nanoparticles (NPs) in samples with different Ni concentrations was investigated by performing a detailed characterization of their structural and magnetic properties. From the determination of several physical parameters of Ni NP assemblies, it was found that the ac and dc magnetic susceptibility measurements are valuable for identifying the DIs between NPs while hysteresis loops measurements showed to be very insensitive, provided that the strength of the DI field is much smaller than the maximum coercive field. Therefore, the sensitivity of the observed static and dynamical magnetic properties to the effect of weak DI depends on the measurement protocols used.

Polycrystalline La5∕8−yPryCa3∕8MnO3, 0⩽y⩽0.625, samples were synthesized by the solid-state reaction method and studied using x-ray powder diffraction, magnetic susceptibility [χ(T)], and magnetoresistivity [ρ(T,H)] measurements. Some features such as an appreciable thermal hysteresis observed in both ρ(T) and χ(T) curves indicated a competing scenario due to the coexistence of different phases. We have also found that there is a critical region in the phase diagram, for the Pr concentration ranging from ∼0.30 to 0.40, where the magnitude of the insulator to metal transition temperature (TMI), the Curie temperature (TC), the magnetoresistance, and the residual resistivity (ρ0) are characterized by abrupt changes with little increase in y. Our data also indicate that the physical properties of these manganites in this critical region are dominated by a strong competition between coexisting ferromagnetic metallic and charge-ordered insulating phases.