Ames Laboratory; Physics and Astronomy
Ames Laboratory, Physics and Astronomy
Physical Review B
Temperature dependent Fe-57 Mossbauer spectroscopy and specific heat measurements for CaK(Fe1-xNix)(4)As-4 with x = 0, 0.017, 0.033, and 0.049 are presented. No magnetic hyperfine field (i.e., no static magnetic order) down to 5.5 K was detected for x = 0 and 0.017 in agreement with the absence of any additional feature below superconducting transition temperature T-c in the specific heat data. The evolution of magnetic hyperfine field with temperature was studied for x = 0.033 and 0.049. The long-range magnetic order in these two compounds coexists with superconductivity. The magnetic hyperfine field B-hf (ordered magnetic moment) below T-c in CaK(Fe0.967Ni0.033)(4)As-4 is continuously suppressed with the developing superconducting order parameter. The B-hf(T) data for CaK(Fe0.967Ni0.033)(4)As-4 and CaK(Fe0.951Ni0.049)(4)As-4 can be described reasonably well by Machida's model for coexistence of itinerant spin density wave magnetism and superconductivity [K. Machida, J. Phys. Soc. Jpn. 50, 2195 (1981)]. We demonstrate directly that superconductivity suppresses the spin density wave order parameter if the conditions are right, in agreement with the theoretical analysis.
DOE Contract Number(s)
Department of Energy Subject Categories
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
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