Domain Meissner state and spontaneous vortex-antivortex generation in the ferromagnetic superconductor EuFe ₂ (As _0.79 P _0.21 ) ₂

Abstract

Adding ferromagnetism to superconductor leads to spatially patterned phases of spontaneously generated vortex-antivortex pairs.

Microwave analysis of the interplay between magnetism and superconductivity in EuFe2(As1−xPx)2Ghigo1, Torsello2, Gozzelino3 et al. 2019Phys. Rev. ResearchSelf Cite241290View full textAdd to dashboardCite

“…Moreover, the bulky character of this transition, only suggested in Ref. [10], is now confirmed by the microwave bulk-sensitive analysis. The low-temperature χ m peak, specific to the high-frequency characterization, corresponds to a transition between different vortex-antivortex dynamical regimes, to a spin reorientation transition of the Eu 2+ canted ferromagnetic subsystem, or to an interplay between the two phenomena.…”

“…It could also be related to a spin reorientation transition of the Eu 2+ canted ferromagnetic subsystem (spin canting does not give contrast in MFM maps). A spin glass transition should probably be excluded for EuFe 2 (As 1−x P x ) 2 , at least in the investigated doping range, since we observed by MFM a well-defined domain structure, i.e., evidence of long-range ferromagnetic ordering [10].…”

“…Zapf et al [5] observed in EuFe 2 (As 1−x P x ) 2 two distinct magnetic transitions below the superconducting transition temperature T sc , and concluded that magnetic ordering at a higher temperature is associated with the predominant antiferromagnetic interlayer coupling, whereas the transition at lower temperature is identified as the changeover to a spin glass state, where the moments between the layers are decoupled. Recently, a transition to a nanometer-scale striped domain structure upon cooling below T sc has been reported [10,11]. At yet lower temperature and without any externally applied magnetic field, the system spontaneously undergoes a phase transition into a domain vortex-antivortex state characterized by domains with peculiar patterns.…”

Effect of Ni doping on vortex pinning in CaK(Fe1−xNix)Haberkorn1, Xu2, Meier3 et al. 2019Phys. Rev. B184290View full textAdd to dashboardCite

“…The sources of flux pinning include random point defects [15], precipitates [16], planar defects [17], and correlated disorder such as twin boundaries [18]. Notwithstanding the coexistence between superconductivity and magnetism usually present in many Fe-SCs [19][20][21], its influence on the resulting vortex dynamics has been little explored.…”

Self-induced magnetic flux structure in the magnetic superconductor RbEuFe4As4

“…For example, in phosphorus-doped EuFe2As2, the superconductivity appears below Tc~24K, while at the Curie point, Tm~19K, the Eu-spins order ferromagnetically in layers separated by the superconducting FeAs-sheets and align parallel to the c-axis [10]. Recent MFM studies have found that in this material the Meissner state coexists with very fine ferromagnetic domains that are smaller than the penetration depth and at lower temperatures transforms into a vortex-domain state [11,12].…”