Magnetic properties of Co film in Pt/Co/Cr₂O₃/Pt structure

Magnetic properties of Co film in Pt/Co/α-Cr₂O₃/Pt/α-Al₂O₃ structure were investigated. Co layer thickness tCo dependence of perpendicular magnetic anisotropy energy density K reveals that the bulk magnetic anisotropy plays an important role in the system in addition to the interfacial anisotropy. Damping constant α monotonically increases with the decrease of tCo but not proportionally to 1/tCo. Both K and α increase with the increase of Pt layer thickness tPt from 3 nm to 5 nm and keeps almost constant in the tPt range between 5 nm to 20 nm. These results are of importance to understand the magnetization switching behavior driven by the magneto-electric (ME) effect as well as to design the spintronics device using the ME effect.T. V. A. Nguyen, Y. Shiratsuchi, H. Sato, S. Ikeda, T. Endoh, and Y. Endo, AIP Advances 10, 015152 (2020); https://doi.org/10.1063/1.5130439

Giant magnetoelectric effect in an L 2₁-ordered Co₂FeSi/Pb(Mg₁/₃Nb₂/₃)O₃-PbTiO₃ multiferroic heterostructure

We experimentally show a giant magnetoelectric (ME) effect at room temperature in an interfacial multiferroic heterostructure consisting of L2₁-ordered Co₂FeSi and Pb(Mg₁/₃Nb₂/₃)O₃-PbTiO₃ (PMN-PT). Molecular beam epitaxy growth at 400 °C enables us to obtain epitaxial and L2₁-ordered Co₂FeSi films on PMN-PT(001). For the epitaxial Co₂FeSi/PMN-PT heterostructure, the remanent magnetization state can be largely modulated by varying electric fields. We note that the room-temperature ME coupling coefficient (α) is estimated to be 6.0-6.3 × 10 - ⁶ s/m, comparable to the highest α value reported previously. Nonvolatile and repeatable magnetization changes in remanent states are also demonstrated. These results will pave the way for room-temperature electric-field control of the magnetization of half-metallic Heusler alloys in high-performance spintronic devices.T. Usami, S. Fujii, S. Yamada, Y. Shiratsuchi, R. Nakatani, and K. Hamaya, Appl. Phys. Lett. 118, 142402 (2021); https://doi.org/10.1063/5.004409

Effect of Fe atomic layers at the ferromagnet-semiconductor interface on temperature-dependent spin transport in semiconductors

Using artificially controlled ferromagnet (FM)-semiconductor (SC) interfaces, we study the decay of the nonlocal spin signals with increasing temperature in SC-based lateral spin-valve devices. When more than five atomic layers of Fe are inserted at the FM/SC interfaces, the temperature-dependent spin injection/detection efficiency (P inj /det) can be interpreted in terms of the T3/2 law, meaning a model of the thermally excited spin waves in the FM electrodes. For the FM/SC interfaces with the insufficient insertion of Fe atomic layers, on the other hand, the decay of P inj /det is more rapid than the T3/2 curve. Using magneto-optical Kerr effect measurements, we find that more than five atomic layers of Fe inserted between FM and SC enable us to enhance the ferromagnetic nature of the FM/SC heterointerfaces. Thus, the ferromagnetism in the ultra-thin FM layer just on top of SC is strongly related to the temperature-dependent nonlocal spin transport in SC-based lateral spin-valve devices. We propose that the sufficient ferromagnetism near the FM/SC interface is essential for high-performance FM-SC hybrid devices above room temperature.M. Yamada, Y. Shiratsuchi, H. Kambe, K. Kudo, S. Yamada, K. Sawano, R. Nakatani, and K. Hamaya, Journal of Applied Physics 129, 183901 (2021); https://doi.org/10.1063/5.0048321

Significant effect of interfacial spin moments in ferromagnet-semiconductor heterojunctions on spin transport in a semiconductor

Using controlled ferromagnet (FM) -semiconductor (SC) interfaces in SC-based lateral spin-valve (LSV) devices, we experimentally study the effect of interfacial spin moments in FM-SC heterojunctions on spin transport in SC. First-principles calculations predict that the spin moment of FM-SC junctions can be artificially reduced by inserting 3d transition metal V, Cr, or Cu atomic layers between FM and SC. When all-epitaxial FM-SC Schottky-tunnel contacts with a 0.4-0.5-nm-thick V, Cr, or Cu interfacial layer are formed, we find that the spin signals in FM-SC LSV devices are significantly decreased at 8 K. When we increase the interfacial spin moment by inserting an ∼0.3-nm-thick Co layer between FM and SC, the spin signals at 8 K are significantly enhanced again. From these experiments, we conclude that the interfacial spin moments at FM-SC interfaces are one of the important factors to achieve large spin signals even in SC-based spintronic devices.T. Naito, R. Nishimura, M. Yamada, A. Masago, Y. Shiratsuchi, Y. Wagatsuma, K. Sawano, R. Nakatani, T. Oguchi, and K. Hamaya, Significant effect of interfacial spin moments in ferromagnet-semiconductor heterojunctions on spin transport in a semiconductor, Phys. Rev. B 105, 195308

Overexpression of the p53-inducible brain-specific angiogenesis inhibitor 1 suppresses efficiently tumour angiogenesis

The brain-specific angiogenesis inhibitor 1 gene has been isolated in an attempt to find fragments with p53 “functional” binding sites. As reported herein and by others, brain-specific angiogenesis inhibitor 1 expression is present in some normal tissues, but is reduced or lost in tumour tissues. Such data and its particular structure prompted the hypothesis that brain-specific angiogenesis inhibitor 1 may act as a mediator in the local angiogenesis balance. We herein demonstrate that brain-specific angiogenesis inhibitor 1 over-expression suppresses tumour angiogenesis, delaying significantly the human tumour growth in immunodeficient mice. The inhibitory effect of brain-specific angiogenesis inhibitor 1 was documented using our intravital microscopy system, strongly implicating brain-specific angiogenesis inhibitor 1 as a mediator in the control of tumour angiogenesis. In contrast, in vitro tumour cell proliferation was not inhibited by brain-specific angiogenesis inhibitor 1 transfection, whereas some level of cytotoxicity was assessed for endothelial cells. Immunohistochemical analysis of tumour samples confirmed a reduction in the microvessel density index in brain-specific angiogenesis inhibitor 1-overexpressing tumours. At messenger level, moderate changes could be detected, involving the down-regulation of vascular endothelial growth factor and collagenase-1 expression. Furthermore, brain-specific angiogenesis inhibitor 1 expression that was lost in a selection of human cancer cell lines could be restored by wild-type p53 adenoviral transfection. Brain-specific angiogenesis inhibitor 1 should be considered for gene therapy and development of efficient drugs based on endogenous antiangiogenic molecules

Agricultura de precisão no Brasil: avanços, dificuldades e impactos no manejo e conservação do solo, segurança alimentar e sustentabilidade.

De acordo com uma de suas definições, a agricultura de precisão (AP) consiste de um conjunto de princípios e tecnologias aplicados no manejo da variabilidade espacial e temporal associada à produção agrícola, objetivando aumentar a produtividade das culturas e a qualidade ambiental (Pierce & Nowak, 1999). Em termos práticos, envolve a obtenção e processamento de informações detalhadas e georreferenciadas sobre as áreas de cultivo agrícola, visando definir estratégias de manejo mais eficientes, em especial, o uso racional de insumos. Com desenvolvimento recente, a AP foi introduzida no Brasil a pouco mais de uma década, mas apresenta grande potencial de aplicação na produção de grãos e em culturas perenes, o que, certamente, contribuirá de forma positiva para a garantia da segurança alimentar, com sustentabilidade econômica e ambiental. As técnicas associadas à AP despertam crescente interesse no meio científico e entre aqueles que se dedicam à atividade agropecuária no Brasil, incluindo produtores rurais e, principalmente, fabricantes de equipamentos, prestadores de serviços e consultores agrícolas. Áreas muito expressivas, ocupadas sobretudo por culturas anuais e cana-de-açúcar, já são manejadas sob algum enfoque da AP, destacando-se a utilização de amostragem georeferenciada para o mapeamento da fertilidade do solo e posterior aplicação de corretivos e fertilizantes a taxa variável. O impacto mais imediato do tratamento diferenciado das lavouras em relação ao manejo de corretivos e fertilizantes tem sido a possibilidade de economia de insumos comparativamente ao manejo tradicional, no qual se utilizam dosagens uniformes em área total baseadas na condição média de fertilidade do talhão. Apesar de certa euforia observada entre os agricultores, impulsionada pelas vantagens econômicas imediatas e pela intensa propaganda difundida pelas empresas prestadoras de serviços de AP, as ações de pesquisa associadas a essa temática vêm evoluindo em ritmo aquém do desejável, em parte, devido à maior complexidade dos procedimentos experimentais envolvidos nos estudos de AP. Nesse cenário, constata-se uma grande defasagem entre as práticas que vêm sendo utilizadas em larga escala no setor produtivo e o que seriam tecnologias de AP validadas com rigor científico. Neste trabalho, é apresentada uma análise crítica sobre a situação atual da agricultura de precisão no Brasil, com foco no manejo da fertilidade do solo em sistemas de produção de culturas anuais, procurando-se destacar os principais aspectos positivos, as limitações, os benefícios potenciais e a necessidade de pesquisa relacionada a essa importante e inovadora abordagem na atividade agropecuária

Portfólio automação agrícola, pecuária e florestal.

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