In this work,Raman scattering measurements have been performed on the collapsed phase CaCo2As2 crystals.At least 8 Raman modes were observed at room temperature though CaCo2As2 is structurally similar to other 122 com...In this work,Raman scattering measurements have been performed on the collapsed phase CaCo2As2 crystals.At least 8 Raman modes were observed at room temperature though CaCo2As2 is structurally similar to other 122 compounds like BaFe2As2.Two Raman modes are assigned to the intrinsic A1gand B1gof this material system respectively.The other ones are considered to originate from the local vibrations relevant to cobalt vacancies.Careful polarized measurements allow us to clearly resolve the four-fold symmetry of the B1gmode,which put strong constraints on possible point group symmetries of the system with Co vacancies.The temperature-dependent measurements demonstrate that the anomalies in both frequency and width of the B1gmode occur around Neel temperature TN.The anomalies are considered to be related to the gap opening near the magnetic transition.The study may shed light on the structural and magnetic changes and their correlations with superconductivity in 122 systems.展开更多
We report 7SAs NMR studies on single crystals of rare-earth doped iron pnictide superconductor Ca1-xPrxFe2As2. In both cases of x = 0.075, 0.15, a large increase of Vq upon cooling is consistent with the tetragonal-co...We report 7SAs NMR studies on single crystals of rare-earth doped iron pnictide superconductor Ca1-xPrxFe2As2. In both cases of x = 0.075, 0.15, a large increase of Vq upon cooling is consistent with the tetragonal-collapsed tetragonal structure transition. A sharp drop of the Knight shift is also seen just below the structure transition, which suggests the quenching of Fe local magnetism, and therefore offers important understanding of the collapsed tetragonal phase. At even low temperatures, the 1/75 T1 is enhanced and forms a peak at T ≈ 25 K, which may be caused by the magnetic ordering of the Pr3＋ moments or soin dynamics of mobile domain walls.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2012CB921701)the National Natural Science Foundation of China(Grant No.11474357)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China
文摘In this work,Raman scattering measurements have been performed on the collapsed phase CaCo2As2 crystals.At least 8 Raman modes were observed at room temperature though CaCo2As2 is structurally similar to other 122 compounds like BaFe2As2.Two Raman modes are assigned to the intrinsic A1gand B1gof this material system respectively.The other ones are considered to originate from the local vibrations relevant to cobalt vacancies.Careful polarized measurements allow us to clearly resolve the four-fold symmetry of the B1gmode,which put strong constraints on possible point group symmetries of the system with Co vacancies.The temperature-dependent measurements demonstrate that the anomalies in both frequency and width of the B1gmode occur around Neel temperature TN.The anomalies are considered to be related to the gap opening near the magnetic transition.The study may shed light on the structural and magnetic changes and their correlations with superconductivity in 122 systems.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074304 and 11222433)the National Basic Research Program of China (Grant Nos. 2010CB923004 and 2011CBA00112)supported by AFOSR-Multidisciplinary University, ResearchInitiative (Grant No. FA9550-09-1-0603)
文摘We report 7SAs NMR studies on single crystals of rare-earth doped iron pnictide superconductor Ca1-xPrxFe2As2. In both cases of x = 0.075, 0.15, a large increase of Vq upon cooling is consistent with the tetragonal-collapsed tetragonal structure transition. A sharp drop of the Knight shift is also seen just below the structure transition, which suggests the quenching of Fe local magnetism, and therefore offers important understanding of the collapsed tetragonal phase. At even low temperatures, the 1/75 T1 is enhanced and forms a peak at T ≈ 25 K, which may be caused by the magnetic ordering of the Pr3＋ moments or soin dynamics of mobile domain walls.
