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Event 

Title:
Fernando Garcia: Relaxação de spin e flutuações magnéticas
When:
15.03.2012 
Where:
Matéria Condensada Teórica - Niterói
Category:
Seminários

Description

Eu2+ spin relaxation and magnetic fluctuations in EuFe2-xCoxAs2

Fernando Garcia (MPI-Dresden - Alemanha)


The discovery of superconductivity in iron-based pnictides sparked a tremendous surge of interest and research activities. This class of materials displays a high structural and chemical flexibility comprising several closely related structure types based on common layered Fe-pnictogen building blocks. The layered compound EuFe2As2 is an interesting model system where layers of Fe2As2 alternate with Eu layers along the c-axis. They offer an important basis to investigate the effects of well defined local Eu2+ 4f states on the itinerant electronic and magnetic properties of the Fe2As2 layers. To address this subject, we combined Eu2+  electron spin resonance (ESR), dc-susceptibility measurements and band structure calculations of EuFe2-xCoxAs2 (0.1< x <0.75) in an effort to understand the nature of the Eu2+ spin relaxation and its relation with the electronic and magnetic properties of the itinerant subsystem. The ESR experiments were carried out at three resonance fields by using three frequencies (L-, X-, and Q-band). We found that the electronic spin relaxation is well understood in terms of the exchange coupling among the local spins. In turn, the Korringa process has only a marginal role in the Eu2+ spin relaxation. This talk starts with a "crash course" on the field of the iron arsenide superconductors and ESR measurements. Afterwards, we discuss our experiments showing that the Eu2+ spin relaxation is field dependent and under direct influence of the magnetic fluctuations at the Fe2-xCoxAs2 layers. Our results present the Eu2+ ESR to be suitable to probe the spin dynamics of the itinerant subsystem

Venue

Group:
Matéria Condensada Teórica
Street:
IF-UFF
ZIP:
24210-346
City:
Niterói
State:
RJ
Country:
Country: br

Description

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