Coexistence of superconductivity and magnetism in KxFe2−ySe2−zSz (z = 0,0.4)

Abstract

Single crystals KxFe2−ySe2−zSz (z = 0, 0.4) are successfully synthesized by self-flux method with the superconducting transition temperatures Tconset of 31.3 K and 32.8 K, respectively. In contrast to external pressure effect on superconductivity, the substitution of S for Se does not suppress Tc, which suggests that chemical doping may mainly modulate the anion height from the Fe layer rather than compressing interlayer distance. In electron spin resonance (ESR) measurements, a resonance signal arising from the paramagnetic (PM) Fe ions is detected at room temperature for both KxFe2−ySe2 and KxFe2−ySe1.6S0.4 crystals. Upon cooling, the intensity of the spectrum weakens gradually and displays abrupt decrease below 140 K. The resonance signal disappears around 60 K (∼2 Tc), corresponding to the saturation temperature of antiferromagnetic (AFM) order revealed by recent neutron-diffraction study. The evolution of ESR spectrum is discussed by correlating with recent neutron-diffraction and Raman-scattering results, in support of the coexistence of superconductivity and AFM order in KxFe2−ySe2. Moreover, the variation of resonance field with decreasing temperature for KxFe2−ySe1.6S0.4 implies that the doping of S induces local weak ferromagnetism in the parent AFM background.

Source-reported materials — not catalogue approval

Similar papers