Phonon Raman Scattering Study of K_2NiF_4 Type Oxide Superconductors

概要

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La (Pt) and apical oxygen (P2) vibrations along the c-axis, which are ,4n,-syuaarnetry in thetetragonal phase (74/mmm), have been systettaatically investigated for KzNiF,j-type oxide strper-condtrctors; LazCtn0,t+,s (d:O, 0.014, 0.063), Lat.ssSro.?sCuO,u, and SI2RLlO,1. For LazCuO,t..s,with increasing of the excess oxygen concentration (ff), the intensity of P2 decreases exponentially as a function of 75 at room temperattrre. This decrease can be trnderstood by the shieldingeffect due to the doped carriers along the c-axis. With decreasing teunperattrre, the intensityof P3 increases for LazCtrO,j.g53 and Laj.g5Srg.)5Ctu0,j at low tenaperature, xvhile La3CuO,j andSrzRuO,j do not show strch anornaly. This zaaight be explained by the decrease of' the shieldingeffect due to the charge confinement along the c-axis. The appearance of the excess oxygenvibration along the c-axis shows that the transition at about 250 K is due to the ['reezing of' theitineracy of the excess oxygen for La3CuO,j.0(;3.
社団法人日本物理学会の論文
1998-07-15