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The observed H2 and |H| dependence of the magnetoresistance above and below TC, respectively, may be explained by general time-reversal symmetry considerations. We further find empirically that the saturation observed in the magnetoresistance is best fit by a simple resistor in series with a magnetoconductor: ρ(H)=ρ∞+1/(σ0+γ|H|) for T<Tc and ρ(H)=ρ∞+1/(σ0+βH2) for T>TC. This provides a functional form to analyze and predict the magnetoresistance over a wide range of fields. This suggests that the underlying mechanism of ‘‘colossal magnetoresistance ’’ may be magnetoconductive, not magnetoresistive. The magnetoresistance and Hall effects on an annealed epitaxial thin films of La0.67Ca0.33MnO3 were measured at 0.9 TC and 1.1 TC. At low fields, anisotropic magnetoresistance plays a dominant role. The high field Hall effect shows holelike carriers above and below TC. The apparent change in sign at low fields is likely due to the anomalous Hall effect.

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Nanometer size polarized domains were written in a PbZr1−xTixO3 (PZT) thin film using an atomic force microscope (AFM) and the relationship between the polarized domain and the grain of the film was investigated. The polarized domain was formed by applying a pulse voltage to the ferroelectric PZT thin film through a conductive AFM tip. The polarized domain structure was observed by imaging the piezoelectric-induced surface vibration by an AFM with an ac voltage applied between the tip and the bottom electrode of a sample. The polarized domains with a diameter of 50 nm were written within a single grain.

Resistivity measurements on a La0.67Ca0.33MnO3 film are reported for a series of argon anneals at successively higher temperatures. Tc, the ferromagnetic ordering temperature, increases uniformly with increasing annealing temperature and annealing time. Hence, Tc can be tuned by appropriate annealing. In order to fully anneal these samples, i.e., achieve bulk properties, it proves sufficient to anneal them in argon. Further annealing in oxygen produces only minor changes in the resistivity. Data from Tc up to 1200 K show activated conduction with ρ=BTeEa/kT, the temperature dependence predicted by the Emin–Holstein theory of adiabatic polaron hopping. Their model fits both data from the partially annealed and fully annealed samples better than the variable range hopping or semiconductor models which have been used by previous workers. The activation energy Ea and resistivity coefficient B decrease with increasing maximum anneal temperature. These changes, together with the increase in Tc, are consistent with an anneal induced relaxation of the Mn–O–Mn bond angle. The time dependent resistivity during annealing at a fixed temperature follows the equation ρ=ρ0{1−D ln[1+(t−t0)/τ]}, making it possible to acquire data in a reversible regime, and also to obtain an estimate of the annealing activation energy.