Polarized Light Microscopy Study on the Reentrant Phase Transition in a (Ba1 – xKx)Fe2As2 Single Crystal with x = 0.24

Abstract

A sequence of structural/magnetic transitions on cooling is reported in the literature for hole-doped iron-based superconductor (Ba 1 − x K x )Fe 2 As 2 with x = 0.24. By using polarized light microscopy, we directly observe the formation of orthorhombic domains in (Ba 1 − x K x )Fe 2 As 2 (x = 0.24) single crystal below a temperature of simultaneous structural/magnetic transition T N~8 0 K. The structural domains vanish below~30 K, but reappear below T = 15 K. Our results are consistent with reentrance transformation sequence from high-temperature tetragonal (HTT) to low temperature orthorhombic (LTO1) structure at T N~8 0 K, LTO1 to low temperature tetragonal (LTT) structure at T c 25 K, and LTT to low temperature orthorhombic (LTO2) structure at T~15 K.

Doping evolution of the second magnetization peak and magnetic relaxation in (Ba1−xKx)FLiu1, Zhou2, Sun3 et al. 2018Phys. Rev. BSelf Cite13170View full textAdd to dashboardCite

“…The similar feature had been observed in Ba(Fe 1−x Co x ) 2 As 2 , where the presence of fine orthorhombic structure domains leads to the J c maximum [10]. The orthorhombic structure domains have been directly observed in the parent compounds and underdoped samples by using polarized light microscopy [10,[51][52][53]. In the previous studies on (Ba 1-x K x )Fe 2 As 2 , high J c were observed between 0.25 0.30, and J c exceed 10 5 A/cm 2 at T=25K and H=6 T for x=0.30 [5][6].…”

“…As far as pinning sources are concerned, the formation of structural domains in the orthorhombic phase has been well studied both in Ba(Fe 1−x Co x ) 2 As 2 and (Ba 1-x K x )Fe 2 As 2 by using polarized light microscopy [10,[51][52][53]. The domain walls extend throughout the samples and act as the extended pinning centers.…”

Mechanical detwinning device for anisotropic resistivity measurements in samples requiring dismounting for particle irradiation

“…The temperature-dependent resistivity of the sample used in this study follows previous reports 15,17 with small upturn in ρ(T ) below 60 K signalling tetragonal-to-orthorhonbic phase transition at T C2 and small down-turn feature at 37 K signalling re-entrance of the tetragonal phase at T C4 [18][19][20] . These features in the ρ(T ) lead to clear anomalies in the temperature-dependent resistivity derivative, dρ(T )/dT , see left panels of Fig.…”

“…This stress value naturally varies on cooling, see right panel. The inset shows ρ(T ) of the sample over the whole range up to 300 K, with the resistivity value fixed at ρ(300K) =300 µΩcm 20 . The right panel shows temperature dependence of x =0.25, zoomed in the range of tetragonal to orthorhombic phase transition (left panel).…”

Raman scattering study of the tetragonal magnetic phase in Sr1−xNaxFe2As2 : Structural symmetry and electronic gap

“…(3) Superconductivity competes with the t-SDW phase more strongly than with the o-SDW phase [17,[29][30][31]. Upon cooling from the t-SDW phase into the superconducting phase, the lattice symmetry may even go back to C 2 [29,30,32].…”