~(7)Li nuclear magnetic resonance in the hexairon(III) antiferromagnetic molecular ring Fe6:Li

摘要

The molecular nanomagnet LiFe_(6)(OCH_(3))_(12)(dbm)_(6)B(C_(6)H_(5))_(4)·5CH_(2)Cl_(2) (Fe6:Li in short) is formed by six Fe(III) s=5/2 spins arranged in an almost coplanar ring with antiferromagnetic (AFM) nearest-neighbor coupling constant J/k_(B)～20 K. We report ~(7)Li nuclear magnetic resonance (NMR) spectra and nuclear spin-lattice relaxation rate (NSLR) measurements as a function of temperature from 1.5 to 50 K with applied field H=1.5 T. No evidence of quadrupole effects was found on the ~(7)Li NMR spectrum within the linewidth resolution (～25 kHz) ruling against a molecular distortion. The ~(7)Li NSLR is compared with the ~(1)H NSLR results in Fe6:Li and in other AFM rings.