One of the most direct evidence for absence of magnetic ordering give NMR or μSR experiments. If there is a local magnetic field present, the nuclear or muon spin would be affected which can be measured. H-NMR measurements on κ-(BEDT-TTF)Cu(CN) have shown no sign of magnetic ordering down to 32 mK, which is four orders of magnitude smaller than the coupling constant J≈250 K between neighboring spins in this compound. Further investigations include:
* Specific heat measurements give information about the low-energy density of states, which can be compared to theoretical models.
* Thermal transport measurements can determine if excitations are localized or itinerant.
* Neutron scattering gives information about the nature of excitations and correlations (e.g. spinons).
* Reflectance measurements can uncover spinons, which couple via emergent gauge fields to the electromagnetic field, giving rise to a power-law optical conductivity.