Emergence of superconductivity and magnetic ordering tuned by Fe-vacancy in alkali-metal Fe chalcogenides RbxFe2-ySe2

27th International Conference on Low Temperature Physics

Kobayashi, Yoshiaki^1 ; Kototani, Shouhei^1 ; Itoh, Masayuki^1 ; Sato, Masatoshi^2

Nagoya University, Furo-cho, Chikusa-ku, Nagoya

464-8602, Japan^1

Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society (CROSS), 162-1 Shirakata, Tokai

319-1106, Japan^2

关键词: Antiferromagnetic transition;    Magnetically actives;    NMR measurements;    NMR spectrum;    Ordered phase;    Paramagnetic phase;    Three phasis;    Vacancy concentration;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/568/2/022024/pdf
DOI  :  10.1088/1742-6596/568/2/022024

来源: IOP

【 摘 要 】

Samples of RbxFe2-ySe2exhibiting superconductivity [superconducting (SC) samples] undergo a phase-separation into two phases, a Fe-vacancy ordered phase with antiferromagnetic (AFM) transition at TN1∼500 K (AFM1 phase) and a phase with little Fe- vacancy and SC transition at Tc∼30 K (SC phase). The samples of RbxFe2-ySe2exhibiting no SC behaviour (non-SC samples) are phase-separated into three phases, The AFM1 phase, another AFM phase with TN2∼150 K (AFM2 phase), and a paramagnetic phase with no SC transitions (paramagnetic non-SC phase). In this paper, we present The experimental results of magnetic susceptibility, electrical resistivity, and NMR measurements on single crystals of RbxFe2-ySe2to reveal physical properties of these co-existing phases in The SC and non-SC samples. The87Rb and77Se NMR spectra show that The Fe vacancy concentration is very small in The Fe planes of The SC phase, whereas The AFM2 and paramagnetic non-SC phases in non-SC samples have larger amount of Fe vacancies. The randomness induced by The Fe vacancy in The non-SC samples makes The AFM2 and paramagnetic non-SC phases insulating/semiconducting and magnetically active, resulting in The absence of The superconductivity in RbxFe2-ySe2.