High-vacuum annealing reduction of Co/CoO nanoparticles.

Porous films of Co/CoO magnetic nanoparticles have been obtained by inert gas condensation and partially oxidized in situ in the deposition chamber. These nanoparticle films were subjected to thermal treatments in high vacuum and the chemical and structural changes monitored by x-ray diffraction, transmission electron microscopy, transport and magnetic measurements (with a focus on the exchange-bias phenomenon), which evidence that for vacuum annealing temperatures above 360 °C, most of the CoO phase is reduced to metallic Co without requiring the presence of an external reducing agent (e.g., H2) or a plasma. Additionally, there is a certain degree of particle coalescence resulting in the formation of greater nanoparticles as the annealing temperature increases. This yields a smaller proportion of CoO compared to metallic Co and a reduction of the Co/CoO interface density, pinpointed by a drastic decrease of the exchange-bias field. The crucial roles of the vacuum level and the surface-to-volume ratio are evidenced by magnetic measurements, highlighting the potential of magnetometry as a probe for the reduction/oxidation of composite nanostructures.

The oxidation of metal-capped Co cluster films under ambient conditions.

We report on the unexpected deterioration under ambient conditions of films of Co clusters capped with relatively thick (>100 nm) Cu (or Ti) layers deposited by either thermal evaporation or by radiofrequency sputtering. The magnetic character of the clusters, prepared by gas-phase condensation, allows monitoring the oxidation of the samples through the decay of the saturation magnetization, which takes place on a timescale of days. By contrast, diluted (<10 at.%) cluster-assembled granular Co:Cu films, prepared by co-deposition of the Co clusters with a Cu vapour, are perfectly stable under ambient conditions. We tentatively explain the oxidation of the cluster films as stemming from their very high porosity.

Multiple-goal pursuit and its relation to cognitive, self-regulatory, and motivational strategies.

BACKGROUND: The topic of academic goals has provided very important information about students' motivation. Traditional research has described several mutually exclusive goals that elicit different motivational patterns. Nevertheless, goal-orientation research has reported the possibility that more than one goal may operate simultaneously. AIM: The purpose of this study was to characterise multiple-goal groups of students, who use various types of cognitive, self-regulatory, and motivational strategies. SAMPLE: Participants were 595 Spanish-speaking university students at the University of A Coruña. METHOD: In order to examine the relationships between goal orientations and strategies, a Pearson correlational analysis was performed. Then, a cluster analysis was performed to identify potential subgroups of students with more than one simultaneously operative goal. Finally, a one-way test was conducted to determine whether the multiple-goal clusters differed in any of the nine strategies. RESULTS: Only those students who reported high task orientation tended to exhibit more frequent use of cognitive and self-regulatory strategies. Nevertheless, this does not mean that learning processes are only optimised by task orientation. When multiple-goal adoption was considered, students who developed the most positive self-regulation were characterised by their focus on learning, but also by their desire to avoid being judged negatively by others. CONCLUSIONS: Students should not adopt only task goals, which are sometimes overvalued, but also other kinds of goals that allow them to manage their learning and make it more flexible in each situation. This aspect characterises self-regulated learning, which is defined not only by cognitive and behavioural regulation but also by motivational regulation.