Thermal entanglement witness for materials with variable local spin lengths

We show that the thermal entanglement in a spin system using only magnetic susceptibility measurements is restricted to the insulator materials. We develop a generalization of the thermal entanglement witness that allows us to get information about the system entanglement with variable local spin lengths that can be used experimentally in conductor or insulator materials. As an application, we study thermal entanglement for the half-filled Hubbard model for linear, square and cubic clusters. We note that it is the itinerancy of electrons that favors the entanglement. Our results suggest a weak dependence between entanglement and external spin freedom degrees.Comment: 4 pages, 3 figure

Magnetic exchange mechanism for electronic gap opening in graphene

We show within a local self-consistent mean-field treatment that a random distribution of magnetic adatoms can open a robust gap in the electronic spectrum of graphene. The electronic gap results from the interplay between the nature of the graphene sublattice structure and the exchange interaction between adatoms.The size of the gap depends on the strength of the exchange interaction between carriers and localized spins and can be controlled by both temperature and external magnetic field. Furthermore, we show that an external magnetic field creates an imbalance of spin-up and spin-down carriers at the Fermi level, making doped graphene suitable for spin injection and other spintronic applications.Comment: 5 pages, 5 figure

Impurities near an Antiferromagnetic-Singlet Quantum Critical Point

Heavy fermion systems, and other strongly correlated electron materials, often exhibit a competition between antiferromagnetic (AF) and singlet ground states. Using exact Quantum Monte Carlo (QMC) simulations, we examine the effect of impurities in the vicinity of such AF- singlet quantum critical points, through an appropriately defined impurity susceptibility, $\chi_{imp}$. Our key finding is a connection, within a single calculational framework, between AF domains induced on the singlet side of the transition, and the behavior of the nuclear magnetic resonance (NMR) relaxation rate $1/T_1$. We show that local NMR measurements provide a diagnostic for the location of the QCP which agrees remarkably well with the vanishing of the AF order parameter and large values of $\chi_{imp}$. We connect our results with experiments on Cd-doped CeCoIn$_5$

Desempenho produtivo de ovinos em pastagem de capim-buffel na estação seca no Semiárido pernambucano.

As pastagens de capim-buffel est„o entre os principais recursos forrageiros para a alimentação de ruminantes no Semi·rido Tropical brasileiro. Entretanto, n„o h· qualquer proposta de manejo do pastejo dessa cultura a fim de promover melhor utilizaÁ„o pelos animais. O estudo objetivou avaliar o desempenho produtivo de ovinos sem padrão racial definido (SRD), mantidos sob diferentes ofertas de biomassa em pastagens de capim-buffel durante a estaÁ„o de baixa precipitação pluviomÈtrica. Foram utilizados 54 ovinos machos, castrados, com peso mÈdio inicial de 19,48 kg. Os tratamentos foram constituÌdos pela combinaÁ„o de duas cultivares de capim-buffel (ëBiloelaí e ëCpatsaí) e trÍs ofertas de biomassa (4,8 e 12 kg de matÈria seca para cada 100 kg de peso vivo/dia). A oferta de biomassa foi calculada com base na matÈria seca total da vegetaÁ„o. O delineamento experimental utilizado foi o de blocos completos casualizados com trÍs repetiÁ?es, em arranjo fatorial 3 x 2. Foi utilizado o mÈtodo de pastejo contÌnuo com oferta de biomassa fixa e taxa de lotaÁ„o vari·vel. Observaram-se maiores (P<0,05) ganhos de peso total e ganho mÈdio di·rio na oferta de biomassa de 12% de matÈria seca independente da cultivar utilizada e menores ganhos na oferta de 4%

Desempenho agronômico de cultivares de batata-doce em Palmas, TO.

O presente trabalho teve como objetivo avaliar o desempenho agronômico de oito cultivares utilizando mudas que passaram pela limpeza clonal.Suplemento. Edição dos Anais do 53 Congresso Brasileiro de Olericultura