Non-adiabatic spin torque investigated using thermally activated magnetic domain wall dynamics

Using transmission electron microscopy, we investigate the thermally activated motion of domain walls (DWs) between two positions in permalloy (Ni80Fe20) nanowires at room temperature. We show that this purely thermal motion is well described by an Arrhenius law, allowing for a description of the DW as a quasi-particle in a 1D potential landscape. By injecting small currents, the potential is modified, allowing for the determination of the non-adiabatic spin torque: the non-adiabatic coefficient is 0.010 +/- 0.004 for a transverse DW and 0.073 +/- 0.026 for a vortex DW. The larger value is attributed to the higher magnetization gradients present

On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films

The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces

Traditional Stream-Border Agriculture in the Dry Forest at the North Coast in Peru: Case Study Jaguay Negro and Casitas

En la zona de amortiguamiento de la Reserva de la Biosfera del Noroeste, al norte del Perú, se practica una agricultura tradicional conocida como «orillado», en el cauce de las quebradas temporales que se forman en la época de avenida. Luego de las lluvias, cuando el cauce ha aminorado, se siembran aquí cultivos estacionales. Se trae la tierra de la pendiente de la quebrada, sobre la cual se desarrollan árboles de la familia Fabaceae, con esta se construyen los surcos. El suelo del surco es removido por el agua de avenida todos los años, y renovado antes de la siembra. Se plantea la siguiente hipótesis: el suelo utilizado en el orillado posee mayor contenido de nitrógeno y fósforo que el suelo del cauce, debido a la presencia de simbiosis microbiana característica de los árboles de la familia Fabaceae que crecen en la orilla de la quebrada. La metodología empleada es mixta, esta incluye entrevistas semiestructuradas y análisis de suelo.Las entrevistas fueron realizadas en los poblados de Jaguay Negro- El Papayo, donde se utiliza la técnica de orillado, y en Casitas-Cherrelique, donde se cultiva directamente en el suelo de la quebrada. El suelo para los análisis fue colectado en los campos de los agricultores de ambos poblados. Los resultados confirman la hipótesis planteada. Los análisis de suelo muestran valores mayores para la zona de Jaguay Negro. Ello comprobaría la hipótesis de que la agricultura de orillado aprovecha la simbiosis microbiana y la de micorrizas y en tal sentido es una agricultura ecológica.The studied area is in the buffer zone of the Northwest Biosphere, in the Peruvian northwest. In this place, traditional agriculture is practiced in the riverbed during the flood time. After the rainy season, when the flood reduces, between April and June, crops are cultivated. The soil is translocated from the slope, were the Prosopis trees grow. The hypothesis is that the soil used for traditional agriculture includes more nitrogen and phosphorus, on the basis of the microbial and fungi symbiosis characteristic for the Fabaceae family. This soil will be removed by the flood. The study was conducted in Jaguay Negro, where the soil was transported from the slope, and in Casitas, where the agriculture uses soil from the gully. Interviews and soil fertility were analyzed. The result shows nitrogen and phosphorus in a middle level, which, as for the dry ecosystem, has a positive influence for the symbioses. This practice of orillado can be interpreted as a form of ecological agriculture since it uses the microbial symbiosis and mycorrhizal fungi. The orillado can be interesting as a resilient response from the local populationto the Climate Change

Observation of thermally-induced magnetic relaxation in a magnetite grain using off-axis electron holography

A synthetic basalt comprising magnetic Fe3O4 grains (~ 50 nm to ~ 500 nm in diameter) is investigated using a range of complementary nano-characterisation techniques. Off-axis electron holography combined with in situ heating allowed for the visualisation of the thermally-induced magnetic relaxation of an Fe3O4 grain (~ 300 nm) from an irregular domain state into a vortex state at 550˚C, just below its Curie temperature, with the magnetic intensity of the vortex increasing on cooling