Magnetic anisotropy in the exchange-biased laser-patterned thin Co/CoO films.

Materials exhibiting an exchange bias effect are a class of magnetic systems that have a wide range of possible technological applications e.g. in sensors, read heads, and spintronic devices. In this study, we demonstrate the effect of laser interference patterning on the magnetic properties of Pd/CoO/Co/Pd multilayers. Laser patterning creates arrays of well-ordered stripes, rectangles, and squares on the substrate surface. We found that the laser treatment caused magnetic softening of the structure edges while the centers of the objects remained unchanged and exhibited the exchange bias effect. In this study we focused on the shape and configurational magnetic anisotropies induced by patterning and showed that the magnetic properties varied depending on the angle at which the external magnetic field was applied with respect to the pattern geometry.

Solvent-particles interactions during composite particles formation by pulsed laser melting of α-Fe2O3.

This work thoroughly investigates chemical solvent-particles interactions during the formation of composite particles by pulsed laser melting of α-Fe2O3. Two solvents, with different dielectric constants, such as ethyl acetate (εr = 6) and ethanol (εr = 24.6), were examined in terms of their effect on the morphology, size, and phase composition of iron oxide composites. We calculated the laser fluence curves using the heating-melting-evaporation approach to identify the critical particle size that undergoes the phase changes first. We assessed the temperature of the particles irradiated with 390 mJ/pulse.cm2 in both solvents, including the heat dissipation between the particles and the liquid. The phase diagram of the Fe-O-C-H system was calculated to determine the temperature-pressure relationship of the system in equilibrium. We also employed an in situ GC-MS analysis to identify the volatile products during irradiation. Based on our experimental results, we concluded that the final diameter of the composites increases from 400 to 600 nm, along with the decreasing dielectric constant of the solvent, which is related to the different polarization of the organic liquid and the degree of particle agglomeration. The reduction of hematite in ethanol proceeded much faster, ending up with Fe/FeCx, while in ethyl acetate, it ended up with Fe3O4. Among all the particles, those with a diameter of 200 nm have the highest temperature and undergo the phase transition first. The temperature of a 200 nm composite particle in ethanol is slightly lower than in ethyl acetate, i.e. 1870 K as compared to 1902 K. Phase equilibrium diagrams proved the existence of Fe, FeO, and Fe3O4 as the preferred phases at about 1900 K. Our research provides a new insight into the process of submicron particle formation during pulsed laser irradiation and allows proposing a mechanism for the growth of particles of different size and phase composition depending on the solvent.

Communication and contraceptive practices in adolescent couples.

This study presents a descriptive analysis of the content, frequency, and timing of couple communication regarding birth control among stable, sexually active adolescent couples, and the effect of communication on actual contraceptive practices. The sample consisted of 83 couples in which the female partner was 15-18 years old. All couples had been sexually active at least two months prior to the interview. The majority of couples had discussed birth control on at least one occasion, but discussions prior to first intercourse were atypical. Couples with good communication patterns were more likely to practice effective contraception. One-fourth of the respondents felt that contraception had not been adequately discussed, and these individuals were found to be most at risk to an unintended pregnancy.

PIP: This study presents a descriptive analysis of the content, frequency, and timing of couple communication regarding birth control among stable, sexually active adolescent couples in the Greater Boston area, and the effect of communication on actual contraceptive practices. The sample consists of 83 couples in which the female partner was 15-18 years old. All couples had been sexually active at least 2 months prior to the interview. The majority of couples had discussed birth control on at least 1 occasion, but discussions prior to 1st intercourse were atypical. Couples with good communication patterns were more likely to practice effective contraception. 1/4 of the respondents felt that contraception had not been adequately discussed, and these individuals were found to be most at risk to an unintended pregnancy. Couples were recruited by means of a public service announcement aired on several rock stations in the Greater Boston area. Each teenager was paid US$20 for participating in the study. The 83 couples were heterogeneous with respect to socioeconomic status, type of residence and personal ambitions. Respondents were from large cities with over 100,000 population (33.7%) as well as small towns of under 25,000 (38%). 70% of respondents had spent their childhood in 2-parent families, although only 40% resided in 2-parent households when interviewed. 51% were Catholics and 52% expected a college education. The mean age was 16.9 for girls and 18.5 for boys. The couples were interviewed separately, but simultaneously for 1-1 1/2 hours. 3 forms of data were used: 1) a topic guide to gather information about the subjects' living arrangements, family and friendship patterns; 2) an interview schedule consisting of 124 questions on the subjects' sexual activity, contraceptive knowledge and practices, and communication; 3) 52 Likert-type items designed to measure attitudes toward birth control, risk-taking, self-esteem, goal orientation, communicativeness, and couple intimacy. Results clearly indicate that conversations per se about birth control were not sufficient to cause couples to practice effective birth control e.g. the pill. Even frequency of such discussions was not a determinative factor. Rather, the quality of the interaction was more important to decision-making. The most commonly reported type of discussion focused on whether or not the girl should go on the pill. Effective communication may not lead to joint decision-making and hence to effective contraception, but may represent a means of negotiating acquiescence once a decision has been made by 1 partner. A cognitive/behavioral approach may be useful in teaching decision-making.