N-type electric conductivity of nitrogen-doped ultrananocrystalline diamond films

Competition between Antiferromagnetism and Superconductivity in the Electron-Doped Cuprates Triggered by Oxygen Reduction

“…Indeed, these studies revealed two main defects appearing with the oxygen reduction, which have been tentatively assigned to out-of-plane and inplane oxygen vacancies, the latter being the only one observed at optimal doping. In parallel, a (RE,Ce) 2 O 3 impurity phase epitaxial to the CuO 2 planes appears in reduced superconducting samples but disappears in reoxygenated nonsuperconducting samples [8,9,10,11]. Based on this phenomenon, it has been proposed recently that the Cu excess released during the formation of the (RE,Ce) 2 O 3 impurity phase fills Cu vacancies and makes the remaining structure more stoichiometric [11].…”

“…In contrast to the widespread belief that the reduction process in the electron-doped cuprates can be considered as an independent degree of freedom for carrier doping, a recent systematic study of the Hall coefficient in Pr 2−x Ce x CuO 4 thin films with various oxygen contents showed that the carrier mobility rather than their concentration is modified by the reduction process [12]. In particular, the annealing process leads to the delocalization of holelike carriers, most likely due to the suppression of the long-range AF order [10,13]. Understanding how the reduction process can tune the competition between the AF and superconducting states and modify the electronic band structure is thus crucial.…”

High-Energy Spin Excitations in the Electron-Doped SuperconductorPr0.88LaCe0.12CuO4−δwithTcWilson1, Li2, Woo3 et al. 2006Phys. Rev. Lett.5514681View full textAdd to dashboardCite

“…Assuming as-grown insulating PLCCO has similar AF exchange coupling as Pr 2 CuO 4 [4], our data suggest that the high energy spin fluctuations in electron-doped PLCCO disperse faster than the spin waves of the insulating compound. Therefore they are unlikely to arise from the weak static AF order in the material [21].…”

“…We chose first to study underdoped PLCCO (T c ∼ 21 K, T N ∼ 40 K) for two reasons. First, this material is between the as-grown AF insulator and optimally doped PLCCO and therefore has a larger magnetic signal than that of the optimally doped PLCCO [21,22,23,24]. Second, Pr 3+ possesses a nonmagnetic singlet ground state in PLCCO, different from the Nd 3+ magnetic ground state in NCCO [25].…”

“…Unfortunately, due to the difficulty of growing large highquality single crystals required for inelastic neutron scattering experiments, there exist only a few studies exploring the low-energy (hω ≤ 10 meV) spin dynamics in electron-doped materials such as Nd 1.85 Ce 0.15 CuO 4 (NCCO) [19,20], and consequently the overall magnetic response of electron-doped materials remains largely unknown. Recently, we began to systematically investigate the evolution of AF order and magnetic excitations as Pr 0.88 LaCe 0.12 CuO 4−δ (PLCCO) is transformed from the as-grown AF insulator into an optimally electrondoped superconductor (T c = 25 K) without static AF order through an annealing process with a minor oxygen content δ modification [21,22,23]. We chose first to study underdoped PLCCO (T c ∼ 21 K, T N ∼ 40 K) for two reasons.…”