Seminarium ACMiN

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Akademickie Centrum Materiałów i Nanotechnologii AGH zaprasza na seminarium, które odbędzie się 7 września 2015 br. o godz. 10.00.

 

Referat pt. „Correlations between Superconductivity and Magnetism: Magneto-transport experiments in RuSr₂GdCu₂O₈ e FeSe_0.5Te_0.5” wygłosi prof. dr. Jorge Luiz Pimentel Jr. (Instytut Matematyki, Uniwersytet Federalny w Rio Grande).

 

Miejsce: ul. Kawiory 30, bud. D-16, sala audytoryjna ACMiN (1.02A).

 

„Correlations between Superconductivity and Magnetism: Magneto-transport experiments in RuSr₂GdCu₂O₈ e FeSe_0.5Te_0.5”

 

This work presents an experimental study of magnetic and magneto-transport properties of systems characterized by correlations between superconductivity and magnetism. Such systems are polycrystalline samples of rutenocuprate RuSr₂GdCu₂O₈ and textured samples of iron-chalcogenide FeSe_0.5Te_0.5. Three distinct heat treatment were used in the preparation of RuSr₂GdCu₂O₈ studied samples. In this system, was possible to isolate the contribution to the magnetization due to ruthenium subnet. It’s allowed the estimative for the effective magnetic moment for this subsystem in the paramagnetic regime of the studied samples. Magneto-transport properties was studied through magnetoresistance and Hall Effect experiments in superconducting and normal phases. The electrical transport in the normal phase has a strong contribution from Ru-O atomic plans, which are considerably affected by the magnetism that stabilizes there. Effects of spin disorder suppression are observed. We also discuss the process of conduction by two bands model and the possible stabilization of ferromagnetic polarons generated by valence fluctuating of Ru. A study of magneto-transport and magnetization was also performed in FeSe_0.5Te_0.5 superconducting samples. The FeSe_0.5Te_0.5 system shows a resistivity behavior that resembles the phenomenology of the Kondo type network. At high temperatures the transport is incoherent and predominantly done by hopping. We propose that electronic resonances occur at sites of Fe by the hybridization effect between electron and hole bands. This corresponds to strong variations in the electron density around the Fe sites, that promotes with decrease of the temperature a progressive formation of the local magnetic moments. Seebeck Effect results in this sample reinforce this interpretation. In this system, the temperature dependence of Hall coefficient in the normal phase reveals the occurrence of fluctuations related to the spin electronic resonance formation at the site of Fe.

 

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