2009/03/16 by V. A. Sidorov, V A Sidorov, A. V. Tsvyashchenko +3
Materials Science · Physics and Astronomy · #Antiferromagnetism #Diamagnetism #Electrical resistivity and conductivity #Hydrostatic pressure #Iron-based superconductors research #Magnetic susceptibility #Magnetism #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #Superconductivity #Tetragonal crystal system #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1088/0953-8984/21/41/415701
arxiv created 2009/03/16 · openalex publication_date 2009/09/23 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We synthesized tetragonal α-FeSe by melting a powder mixture of iron and selenium at high pressure. Subsequent annealing at normal pressure results in removing traces of hexagonal β-FeSe, formation of a rather sharp transition to a superconducting state at T(c)∼7 K, and the appearance of a magnetic transition near T(M) = 120 K. Resistivity and ac-susceptibility were measured on the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic transition visible in ac-susceptibility shifts down under pressure and a resistive anomaly typical for a spin density wave (SDW) antiferromagnetic transition develops near the susceptibility anomaly. T(c), determined by the appearance of a diamagnetic response in susceptibility, increases linearly under pressure at a rate dT(c)/dP = 3.5 K GPa(-1). Below 1.5 GPa, the resistive superconducting transition is sharp, the width of transition does not change with pressure and, T(c), determined by a peak in dρ/dT, increases at a rate ∼3.5 K GPa(-1). At higher pressure, a giant broadening of the resistive transition develops. This effect cannot be explained by possible pressure gradients in the sample and is inherent to α-FeSe. The dependences dρ(T)/dT show a signature for a second peak above 3 GPa which is indicative of the appearance of another superconducting state in α-FeSe at high pressure. We argue that this second superconducting phase coexists with SDW antiferromagnetism in a partial volume fraction and originates from pairing of charge carriers from other sheets of the Fermi surface.