ABSTRACT
Pulse laser deposited La2/3Sr1/3MnO3 ultrathin films on SrTiO3 substrates were characterized by polar and longitudinal Kerr magneto-optical spectroscopy. Experimental data were confronted with theoretical simulations based on the transfer matrix formalism. An excellent agreement was achieved for a 10.7 nm thick film, while a distinction in the Kerr effect amplitudes was obtained for a 5 nm thick film. This demonstrated the suppression of ferromagnetism due to the layer/substrate interface effects. A revised, depth-sensitive theoretical model with monolayer resolution described the experimental data well, and provided clear cross-section information about the evolution of ferromagnetism inside the film. It was found that the full restoration of the double-exchange mechanism, responsible for the ferromagnetic ordering in La2/3Sr1/3MnO3, occurs within the first nine monolayers of the film. Moreover, all the studied films exhibited magneto-optical properties similar to bulk crystals and thick films. This confirmed a fully developed perovskite structure down to 5 nm.
ABSTRACT
We demonstrate that the propagation velocity of field driven magnetic domain walls in ultrathin Au/Co/Au films with perpendicular anisotropy on vicinal substrates is anisotropic and strongly depends on the step density of the substrate. The velocity of walls oriented perpendicular to the steps drastically increases with increasing local step density while being unchanged or only weakly decreased for the walls oriented parallel to the steps. We develop an analytical model revealing the step-modified exchange interactions as the main driving force for this anisotropic behavior. The enhancement of the domain wall velocity at low magnetic fields far below the Walker instability threshold makes this phenomenon interesting for magnetic nanodevices.
ABSTRACT
UNLABELLED: France was the first country to promote the extensive use of buprenorphine for the treatment of drug-addicted subjects through the primary care system. To assess both professional commitment and patients' characteristics, all the physicians and pharmacists of a French area having prescribed/dispensed buprenorphine from 2/12/96 (the official release date) to 1/31/98 were identified from data files of the Health Insurance and then interviewed. During the first 61 weeks of buprenorphine maintenance treatment (BMT), 27.5% of physicians and 51.2% of pharmacists of that area were involved; 142 patient records were documented. Features of the clinical routines spontaneously implemented for practice-based BMT were: a high level of on-site supervised dispensation by the pharmacist (71% at treatment induction and 23% thereafter); the absence of objective measurement of illicit drug use; and a low buprenorphine dosage. These features are consistent with the lack of physicians' experience and training, and also the relatively good status of the population treated (no HIV-positives, heroin use duration averaging 4.2 +/- 3.1 years, and 81.7% with stable accommodations). Despite liberal regulations guiding BMT, a negligible proportion of cases had a "nomadic" attitude (multiple buprenorphine prescribers/deliverers). The treatment outcomes (no deaths, three drug overdoses, improvement in occupational status) are encouraging. CONCLUSION: Practice-based BMT appears to be a safe and acceptable response to moderate heroin addiction, but further training of the professionals involved and longitudinal investigations of individual outcomes are needed.
