Superconducting La2CuO4-δFy samples were synthesized by heating La2CuO4 together with a fluorinating reagent, NH4F, at 240°C in flowing oxygen gas. Bulk superconductivity with Tc = 42 K in the samples was confirmed by DC magnetic susceptibility measurements. The enhancement in the orthorhombicity of the K2NiF4 phase (a = 5.319 Å, b = 5.442 Å, c = 13.20 Å) was observed. The lower and upper critical fields, Hc1(0) and Hc2(0), for the La2CuO4-δFy were roughly determined to be 98 Oe and 600 kOe, respectively.
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