We use inelastic neutron scattering to establish the modulation vectors δ and correlation lengths for the incommensurate magnetic fluctuations in metallic samples of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ with x=0.075 and 0.14. In notation appropriate for a square lattice where the magnetic instability in the undoped case occurs at (π,π), the vectors δ are along (π,0) and (0,π). The correlation length ξ is larger than the distance between carriers, is weakly dependent on x, and changes significantly between 12 and 100 K for both compositions.

The magnetic structures of the hexagonal ${\mathrm{YMnO}}_3$ and ${\mathrm{ScMnO}}_3$ oxides (space group ${P6\mathrm{}}_{3}cm)$ have been studied by neutron-diffraction experiments on powder samples. This study has been complemented with magnetic susceptibility and specific-heat measurements. They confirm that ${\mathrm{YMnO}}_3$ and ${\mathrm{ScMnO}}_3$ become ordered below $T_N\approx 70$ K and $T_N\approx 129$ K, respectively, according to a triangular antiferromagnetic structure. The latter compound undergoes a second magnetic transition below 75 K, corresponding to a spin reorientation. The presence of weak ferromagnetism of Dzialoshinskii-Moriya type is observed in all the ordered region for the Sc material. In both compounds the moments are contained in the $\mathrm{}(a,b)\mathrm{}$ plane and oriented perpendicular $(R=\mathrm{Y})$ or parallel $(R=\mathrm{Sc})$ to the [100] directions. The low-temperature ordered moments are $2.90\left(2\right)\mathrm{}{\mu }_B$ $(R=\mathrm{Y})$ and $3.54\left(3\right)\mathrm{}{\mu }_B$ $(R=\mathrm{Sc})$ at $T=1.7\mathrm{}$ K. The different behavior observed in the thermal evolution of the magnetic structure of both compounds is discussed in terms of geometrical parameters determined from high-resolution structural data. The origin of the weak ferromagnetism in ${\mathrm{ScMnO}}_3$ is also analyzed.

We search for general patterns that explain the low field magnetoresistance at low temperatures in the system $A_{(2-x)}{A}_x^{\prime }{\mathrm{FeMoO}}_6$. The observed linear dependence of the low field magnetoresistance with the saturation magnetization for the series is related to the antisite disorder at the $\mathrm{Fe}$ and $\mathrm{Mo}$ sites. This is explained in terms of a spin dependent crossing of intragranular barriers originated from the presence of antiferromagnetic ${\mathrm{SrFeO}}_3$ patches that naturally develop when antisite disorder occurs in the double perovskite. The presence of a moderate level of antisite disorder is at the very root of low field magnetoresistance although effects such as disorder distribution, connectivity, or morphology add their contribution.