Universal Relationship Between Giant Magnetoresistance and Anisotropic Magnetoresistance in Spin Valve Multilayers

We measure the giant magnetoresistance (GMR) with the current both parallel and perpendicular to the direction of the magnetization in the ferromagnetic (FM) layers and thus probe the anisotropy of the effective mean free paths for the spin-up and spin-down electrons, seen in the anisotropic magnetoresistance. We find that the difference of the GMR in the two configurations, when expressed in terms of the sheet conductance, displays a nearly universal behavior as a function of GMR. On interpreting the results within the Boltzmann transport formalism we demonstrate the importance of bulk scattering for GMR.Comment: REVTEX, 2 figure

AC susceptibility and ESR measurements on the Ag : Mn spin glass

We present measurements between 1.2 and 4.2 K, of the AC susceptibility from 93 Hz to 109 kHz, and of the ESR at 1.6 and 9.2 GHz on dilute Ag : Mn spin glasses around TG. Within experimental error, the AC glass temperature is independent of the measuring frequency. The shift of the resonance line can be related to the applied static field but the temperature for a linewidth minimum is the same at both resonance frequencies.On présente des mesures entre 1,2 et 4,2 K de susceptibilité en courant alternatif (AC) à des fréquences allant de 93 Hz à 109 kHz et de RPE à 1,6 et 9,1 GHz sur les verres de spin dilués Ag : Mn autour de T G. Aux erreurs expérimentales près, la température de gel, mesurée en alternatif, est indépendante de la fréquence de mesure. Le déplacement de la raie de résonance peut être relié au champ externe statique mais la température du minimum de la largeur de raie est la même à 1,6 et 9,1 GHz

New example of superconducting walls in the ferromagnet ErRh/sub 4/B/sub 4/

In the ferromagnetic state of ErRh/sub 4/B/sub 4/, a zero resistance is observed in the easy magnetization direction and a normal state resistance in the hard direction. These properties are characteristic of domain wall superconductivity. 7 refs., 2 figs

Quantitative mapping of global land degradation using Earth observations

Land degradation is a global issue on par with climate change and loss of biodiversity, but its extent and severity are only roughly known and there is little detail on the immediate processes – let alone the drivers. Earth-observation methods enable monitoring of land degradation in a consistent, physical way and on a global scale by making use of vegetation productivity and/or loss as proxies. Most recent studies indicate a general greening trend, but improved data sets and analysis also show a combination of greening and browning trends. Statistically based linear trends average out these effects. Improved understanding may be expected from data-driven and process-modelling approaches: new models, model integration, enhanced statistical analysis and modern sensor imagery at medium spatial resolution should substantially improve the assessment of global land degradation