TY - JOUR
T1 - Mössbauer and magnetization studies of A0.8Fe 2-ySe2 (A = K, Rb and K/Tl)
AU - Nowik, I.
AU - Felner, I.
AU - Zhang, M.
AU - Wang, A. F.
AU - Chen, X. H.
PY - 2011/9
Y1 - 2011/9
N2 - 57Fe Mössbauer spectroscopy and dc magnetization studies of the magneto-superconducting tetragonal A0.8Fe2-ySe 2 (A = K, Rb and K/Tl, y = 0.2-0.3) materials at temperatures of 5-550K have been performed. Below the superconducting transition, magnetization studies performed under low applied fields (H), on both Rb0.8Fe 2-ySe2 and K0.3Tl0.5Fe 2-ySe2 single crystals, show a positive field-cooled branch known as the paramagnetic-Meissner effect for but not for . This paramagnetic-Meissner effect is attributed to a peculiar isothermal hysteresis loop obtained for . Despite being superconducting, due to the antiferromagnetic nature of the materials, Mössbauer spectroscopy studies exhibit well-defined sextets at low temperatures. The full diagonalization of the hyperfine interaction spin Hamiltonian shows clearly that the iron moments are tilted by ∼ 40°-45° away from the c-axis of the low-temperature tetragonal type structure. Moreover, long-term Mössbauer spectroscopy measurements at elevated temperatures suppress the antiferromagnetic state, and the materials measured after cooling to ambient temperatures exhibit a paramagnetic doublet only; its origin is discussed.
AB - 57Fe Mössbauer spectroscopy and dc magnetization studies of the magneto-superconducting tetragonal A0.8Fe2-ySe 2 (A = K, Rb and K/Tl, y = 0.2-0.3) materials at temperatures of 5-550K have been performed. Below the superconducting transition, magnetization studies performed under low applied fields (H), on both Rb0.8Fe 2-ySe2 and K0.3Tl0.5Fe 2-ySe2 single crystals, show a positive field-cooled branch known as the paramagnetic-Meissner effect for but not for . This paramagnetic-Meissner effect is attributed to a peculiar isothermal hysteresis loop obtained for . Despite being superconducting, due to the antiferromagnetic nature of the materials, Mössbauer spectroscopy studies exhibit well-defined sextets at low temperatures. The full diagonalization of the hyperfine interaction spin Hamiltonian shows clearly that the iron moments are tilted by ∼ 40°-45° away from the c-axis of the low-temperature tetragonal type structure. Moreover, long-term Mössbauer spectroscopy measurements at elevated temperatures suppress the antiferromagnetic state, and the materials measured after cooling to ambient temperatures exhibit a paramagnetic doublet only; its origin is discussed.
UR - http://www.scopus.com/inward/record.url?scp=80051961534&partnerID=8YFLogxK
U2 - 10.1088/0953-2048/24/9/095015
DO - 10.1088/0953-2048/24/9/095015
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AN - SCOPUS:80051961534
SN - 0953-2048
VL - 24
JO - Superconductor Science and Technology
JF - Superconductor Science and Technology
IS - 9
M1 - 095015
ER -