NMR study of magnetic moments arising in superconducting cuprates under electron/neutron irradiation

Abstract

The measurements of direct-current magnetic susceptibility and nuclear magnetic resonance (NMR) were performed in the superconducting cuprates YBa 2Cu 3 O69 (89Y, 63 Cu), T12Ba2CaCu2O8 ("O, 205 T1), irradiated by fast neutrons (E 0 = 1 MeV) and electrons (Ee = 5 MeV). The influence of the radiation-induced structural disorder on the spin susceptibility and magnetic state of atoms in the CuO 2 layer is considered. The possible effect on T of the spin-exchange scattering of carriers by localized moments arising under irradiation was estimated following the Abrikosov-Gorkov approach and its contribution was found to be too small in comparison with the real suppression of T under irradiation.

Superconducting properties of the atomically disordered MgB2 compound

“…It was found that TC decreases under irradiation from 6.5 to 2.9 K and completely recovers after annealing at 600 • C. Temperature dependences ρ(T ) are characteristic of compounds with strong electron-phonon interaction. The dHC 2 /dT behaviour testifies to a considerable decrease in density of electronic state at Fermi level N (EF ) in the course of disordering.Radiation-induced disordering caused by irradiation with high-energy particles is a unique method of investigating the properties of superconducting and normal states of ordered crystals [1,2]. Even in broad-band metals, such as intermetallic compounds with A15 structure, long-range ordering loss leads to considerable rearrangement of the electronic spectrum, resulting in disappearance of individual features of the electronic structure.…”

“…Disordering causes decrease in densities at Fermi level N (E F ) and respective noticeable drop of T C in compounds with high initial N (E F ) (Nb 3 Sn or V 3 Si), and considerable (from 1.5 to 7 K) rise of T C in compounds with low N (E F ) and T C due to growth of N (E F ) (Mo 3 Si and Mo 3 Ge) [3,4,5]. In type HTSC compounds, disordering leads to more significant changes in properties: fast and complete T C degradation is accompanied with N (E F ) decrease and metal-insulator transition [2]. Thus investigation of response of a system to radiation-induced disordering serves as a kind of a test to reveal the characteristic features of its electron states.…”

“…Radiation-induced disordering caused by irradiation with high-energy particles is a unique method of investigating the properties of superconducting and normal states of ordered crystals [1,2]. Even in broad-band metals, such as intermetallic compounds with A15 structure, long-range ordering loss leads to considerable rearrangement of the electronic spectrum, resulting in disappearance of individual features of the electronic structure.…”