Low-Field Knight Shift Measurement at Sb Site for Alkaline-Earth Filled Skutterudites AFe_4Sb_<12> (A=Sr and Ca)(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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^<121>Sb Knight shift K measurement has been carried out by applying a perturbing field to the nuclear quadrupole resonance (NQR) spectrum in alkaline-earth filled skutterudites AFe_4Sb_<12> (A=Ca and Sr), which are close to ferromagnetic instability. The hyperfine coupling constant was determined for the first time as -14.9kOe/μ_B f.u. from the K-_χ plot. This relatively large value suggests a strong Fe-Sb covalent bonding. The intrinsic spin susceptibility χ_<spin> derived from K markedly decreases at low temperatures after Curie-Weiss-like increase at high temperatures, which seems to be responsible for the absence of ferromagnetic order. Using the T-dependence of χ_<spin>, the unusual gap-like suppression of nuclear spin-lattice relaxation rate divided by temperature 1/T_1T in our previous report is reasonably explained by assuming the spin dependent-term to be proportional to χ_<spin> and the gap-like suppression of the spin-independent term.
社団法人日本物理学会の論文
2008-06-15