Low-temperature behavior of the ESR linewidth in a system with a spin gap: η − Na 1.286 V 2 O 5

International audienceUsing X-band electron spin resonance ESR spectroscopy down to 4.2 K, we report on the low-temperature magnetic behavior of-Na 1.286 V 2 O 5 , a system with a spin gap. We particularly find that the ESR linewidth of this compound shows an unusual temperature dependence, rich in features. Addressing the problem via the memory function formalism, we propose an explanation for this, whereby we suggest that this unconventional low-temperature behavior is related to the way in which the magnetic susceptibility and the memory function depend on temperature, rather than to a specific magnetic origin