Information transfer by vector spin chirality in finite magnetic chains

Vector spin chirality is one of the fundamental characteristics of complex magnets. For a one-dimensional spin-spiral state it can be interpreted as the handedness, or rotational sense of the spiral. Here, using spin-polarized scanning tunneling microscopy, we demonstrate the occurrence of an atomic-scale spin-spiral in finite individual bi-atomic Fe chains on the (5x1)-Ir(001) surface. We show that the broken inversion symmetry at the surface promotes one direction of the vector spin chirality, leading to a unique rotational sense of the spiral in all chains. Correspondingly, changes in the spin direction of one chain end can be probed tens of nanometers away, suggesting a new way of transmitting information about the state of magnetic objects on the nanoscale.Comment: accepted by Physical Review Letter

Magnetic Properties of Monolayer Co Islands on Ir(111) Probed by Spin-Resolved Scanning Tunneling Microscopy

As the characteristic length scale of devices continues to decrease, it is essential to understand the fundamental magnetic properties of reduced dimension structures. This paper examines the electronic and magnetic properties of two-dimensional nanoscale Co islands on an Ir(111) surface using spin-polarized scanning tunneling microscopy. The pseudomorphic Co islands investigated are ferromagnetic and single domain, with the magnetic easy axis normal to the sample surface. Remarkably, the coercivity of these islands is greater than 4 T and magnetic saturation of the islands requires an applied field of at least 5 T

Magnetic Properties of Monolayer Co Islands on Ir(111) Probed by Spin-Resolved Scanning Tunneling Microscopy

As the characteristic length scale of devices continues to decrease, it is essential to understand the fundamental magnetic properties of reduced dimension structures. This paper examines the electronic and magnetic properties of two-dimensional nanoscale Co islands on an Ir(111) surface using spin-polarized scanning tunneling microscopy. The pseudomorphic Co islands investigated are ferromagnetic and single domain, with the magnetic easy axis normal to the sample surface. Remarkably, the coercivity of these islands is greater than 4 T and magnetic saturation of the islands requires an applied field of at least 5 T

Observation of a Complex Nanoscale Magnetic Structure in a Hexagonal Fe Monolayer

We have observed a novel magnetic structure in the pseudomorphic Fe monolayer on Ir(111). Using spin-polarized scanning tunneling microscopy we find a nanometer-sized two-dimensional magnetic unit cell. A collinear magnetic structure is proposed consisting of 15 Fe atoms per unit cell with 7 magnetic moments pointing in one and 8 moments in the opposite direction. First-principles calculations verify that such an unusual magnetic state is indeed lower in energy than all solutions of the classical Heisenberg model. We demonstrate that the complex magnetic structure is induced by the strong Fe-Ir hybridization

Writing and Deleting Single Magnetic Skyrmions

Topologically nontrivial spin textures have recently been investigated for spintronic applications. Here, we report on an ultrathin magnetic film in which individual skyrmions can be written and deleted in a controlled fashion with local spin-polarized currents from a scanning tunneling microscope. An external magnetic field is used to tune the energy landscape, and the temperature is adjusted to prevent thermally activated switching between topologically distinct states. Switching rate and direction can then be controlled by the parameters used for current injection. The creation and annihilation of individual magnetic skyrmions demonstrates the potential for topological charge in future information-storage concepts

Writing and Deleting Single Magnetic Skyrmions

Topologically nontrivial spin textures have recently been investigated for spintronic applications. Here, we report on an ultrathin magnetic film in which individual skyrmions can be written and deleted in a controlled fashion with local spin-polarized currents from a scanning tunneling microscope. An external magnetic field is used to tune the energy landscape, and the temperature is adjusted to prevent thermally activated switching between topologically distinct states. Switching rate and direction can then be controlled by the parameters used for current injection. The creation and annihilation of individual magnetic skyrmions demonstrates the potential for topological charge in future information-storage concepts

The Kondo Box: A Magnetic Impurity in an Ultrasmall Metallic Grain

We study the Kondo effect generated by a single magnetic impurity embedded in an ultrasmall metallic grain, to be called a ``Kondo box''. We find that the Kondo resonance is strongly affected when the mean level spacing in the grain becomes larger than the Kondo temperature, in a way that depends on the parity of the number of electrons on the grain. We show that the single-electron tunneling conductance through such a grain features Kondo-induced Fano-type resonances of measurable size, with an anomalous dependence on temperature and level spacing.Comment: 4 Latex pages, 4 figures, submitted to Phys. Rev. Let

Impacto na Aprendizagem Envolvendo o Desenvolvimento de Aplicativos na Educação Básica: um Mapeamento Sistemático da Literatura

O ensino de computação na Educação Básica tem se apresentado como uma alternativa para o desenvolvimento de habilidades do século XXI. Vem sendo tipicamente ensinado por meio de linguagens de programação como App Inventor, ferramenta que possibilita o desenvolvimento de aplicativos móveis para smartphones. Porém, ainda não se tem uma compreensão dos impactos que práticas pedagógicas têm gerado na aprendizagem dos alunos com esse enfoque específico no ambiente de programação. O artigo apresenta o resultado de um Mapeamento Sistemático da Literatura em que se buscou analisar os impactos de práticas pedagógicas de desenvolvimento de aplicativos com o App Inventor na aprendizagem de conteúdos curriculares da Educação Básica tanto no Brasil quanto internacionalmente. Os resultados mostram que há práticas realizadas em ambiente de programação em atividades extracurriculares, especialmente no contraturno e em período de férias, indicando que há ainda poucas práticas  interligando o currículo com o App Inventor. Os resultados positivos têm relação com as estratégias metodológicas escolhidas para a aplicação das práticas, cujos melhores resultados estão relacionados aos interesses, aos problemas do cotidiano dos alunos e a partir da formação de professores das instituições. Por outro lado, as dificuldades apontadas envolvem limitações dos alunos em conhecimentos básicos e pouco tempo para o desenvolvimento das atividades