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25Mg NMR study of the MgB2 superconductor

M. Mali, J. Roos, A. Shengelaya, H. Keller, K. Conder

cond-mat.supr-conarXiv:cond-mat/0111022

Abstract

25Mg NMR spectra and nuclear spin-lattice relaxation time, T1, have been measured in polycrystalline 25MgB2 with a superconducting transition temperature Tc = 39.0 K in zero magnetic field. From the first order and second order quadrupole perturbed NMR spectrum a quadrupole coupling frequency nuQ = 222(1.5) kHz is obtained. T1T = 1090(50) sK and Knight shift Kc = 242(4) ppm are temperature independent in the normal conducting phase. The 25Mg Korringa ratio equals to 0.95 which is very close to the ideal value of unity for s-electrons. The comparison of the experimental nuQ, T1T, and Kc with the corresponding values obtained by LDA calculations shows an excellent agreement for all three quantities.

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