Magnetic state and anisotropies in iron based superconductors

DIPC Seminars

María José Calderon, Instituto de Ciencia de Materiales de Madrid CSIC
Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4 (nearby the Facultad de Quimica), Donostia
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Magnetic state and anisotropies in iron based superconductors Fe-based superconductors were discovered early 2008, with the highest superconducting critical temperatures (Tc) ever found after the record holding cuprates. The new superconductors develop the superconducting phase upon doping or applying pressure to a metallic anisotropic antiferromagnetic compound. The similarities with the cuprates (high Tc and antiferromagnetic parent phase) triggered a great deal of attention, which was farther stimulated by the differences (undoped cuprates are Mott insulators, not metals) and by the perceived importance of the multiorbital character of the electronic carriers. The properties of the magnetic phase itself are a subject of a strong debate due to the unexpected low magnetic moment, the different antiferromagnetic orderings encountered (columnar and bi-stripe), and a counter-intuitive resistivity anisotropy. Understanding these properties may be the key to unravel the origin of the superconductivity. I will first present a general overview of these materials and then I will focus on our model studies of the magnetic phase diagram which uncover the importance of the interplay between the spin and orbital degrees of freedom. References: [1] M.J. Calderón, B. Valenzuela, and E. Bascones. Phys. Rev. B 80, 094531 (2009). [2] E. Bascones, M.J. Calderón, and B. Valenzuela. Phys. Rev. Lett. 104, 227201 (2010). [3] B. Valenzuela, E. Bascones, and M.J. Calderón. Phys. Rev. Lett. 105, 207202 (2010).