Abstract
The evolution of low-energy spin dynamics in the iron-based superconductor LaFeAsOF was studied over a broad doping, temperature, and magnetic field range ( 0–0.15, 480 K, 30 T) by means of As nuclear magnetic resonance. An enhanced spin-lattice relaxation rate divided by temperature in underdoped superconducting samples ( 0.045, 0.05, and 0.075) suggests the presence of antiferromagnetic spin fluctuations, which are strongly reduced in optimally doped () and completely absent in overdoped () samples. In contrast to previous analysis, Curie-Weiss fits are shown to be insufficient to describe the data over the whole temperature range. Instead, a Bloembergen-Purcell-Pound (BPP) model is used to describe the occurrence of a peak in clearly above the superconducting transition, reflecting a progressive slowing down of the spin fluctuations down to the superconducting phase transition.
3 More- Received 11 July 2013
DOI:https://doi.org/10.1103/PhysRevB.88.104503
©2013 American Physical Society