Anisotropic superconductivity in Eu(Fe _0.75 Ru _0.25 ) ₂ As ₂ ferromagnetic superconductor

Abstract

We report an unprecedented anisotropic superconductivity in Eu(Fe0.75Ru0.25)2As2 single crystals. The in-plane resistivity (ρ ab ) and vertical magnetization (Mc) show a superconducting transition at TSC = 23 K with zero resistance and magnetic shielding, respectively. In comparison, the out-of-plane resistivity (ρc) does not go to zero, neither does the horizontal magnetization (M ab ) show the shielding against external fields. Magnetization and Mössbauer data indicate that the Eu 2+ spins order ferromagnetically below 19.5 K with the moments tilted 20 • from the c-axis. Our result suggests spontaneous-vortex phase and/or Fulde-Ferrell-Larkin-Ovchinnikov state in the ferromagnetic superconductor.

Phase diagram of Eu magnetic ordering in Sn-flux-grown Eu(Fe1−xCox)2AsJin1, Xiao2, Bukowski3 et al. 2016Phys. Rev. B292460View full textAdd to dashboardCite

“…Such coexistence of strong ferromagentism and superconducivity was also observed in other doped EuFe 2 As 2 compounds including EuFe 2 (As 1−x P x ) 2 , 10,34,51 Eu(Fe 1−x Ru x ) 2 As 2 , 12 and Eu(Fe 1−x Ir x ) 2 As 2 . 13,35,52 Interestingly, in the phase diagram shown in Fig.…”

“…6 This compound exhibits a spin-densitywave (SDW) ordering of the itinerant Fe moments concomitant with a tetragonal-to-orthorhombic structural phase transition below 190 K. In addition, the localized Eu 2+ spins order below 19 K in an A-type antiferromagnetic (AFM) structure (ferromagnetic layers stacking antiferromagnetically along the c direction). 7,8 Superconductivity can be achieved in this system by suppressing the SDW ordering of Fe in the form of chemical substitution [9][10][11][12][13] or applying external pressure. 14,15 For example, by hole doping with partial substitution of K for Eu, Eu 0.5 K 0.5 Fe 2 As 2 shows SC below the superconducting transition temperatureT sc = 32 K. 9 Isovalent substitution of P into the As sites can also give rise to the SC with T sc over 20 K. 10,16 Nevertheless, for the electron-doped Eu(Fe 1−x Co x ) 2 As 2 system, the reports about its physical properties remain quite controversial.…”

Fluence-dependent femtosecond quasiparticle and Eu2+ spin relaxation dynamics in EuFe2(As,P)Pogrebna1, Mertelj2, Cao3 et al. 2016Phys. Rev. B1100View full textAdd to dashboardCite

“…Single crystals of EuFe 2 (As 1−x P x ) 2 were grown by the flux method, similar to the previous report [14]. Small Eu chunks and powders of Fe, As, and P (Alfa Aesar, >99.9%) were mixed together in the molar ratio of Eu:Fe:As:P = 1:5:5(1-x):5x (x is the nominal P content) and sealed in an evacuated quartz ampule.…”

Spectrally resolved femtosecond reflectivity relaxation dynamics in undoped spin-density wave 122-structure iron-based pnictides

“…Single crystals of EuFe 2 As 2 and SrFe 2 As 2 were grown at Zhejiang University by a flux method, similar to a previous report 27 . Small Eu chunks and powders of Fe, As (Alfa Aesar, > 99.9%) were mixed together in the molar ratio of Eu:Fe:As = 1:5:5 and sealed in an evacuated quartz ampoule.…”