| There are serious reasons to believe that the magnetism of high-temperature superconductors (HTSCs) based on layered cuprates is of composite origin. For weak doping, there are localized spins on the copper sites, while the temperature dependence of the spin susceptibility in the overdoped region of the phase diagram can be well described within itinerant magnetism's scenario. The duality of magnetism of YBa2Cu3O6+x compounds is clearly manifested in recent experiments on the inelastic neutron scattering. Near the wave vector Q= (?, ?), two contours ("modes") of maxima were found in the imaginary part of the susceptibility that cannot coexist in the framework of the theory of simple metals and insulators. In this seminar, starting on fermiology like treatment, we first study the momentum and frequency dependence of the dynamical spin susceptibility in the superconducting state of overdoped cuprate superconductors. Then we show how the magnetic structure modifies if one goes towards more underdoped cuprates and propose a universal description for the dynamic spin susceptibility of layered cuprates. It provides a simultaneous description of both itinerant and localized magnetism features observed in the inelastic neutron scattering study of underdoped cuprates. |
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