Phase separation and weak ferromagnetism in lightly-oxygen-doped La2CuO4+x single crystals in low magnetic fields

摘要

Ferromagnetic regions formed in lightly-oxygen-doped La2CuO4+x single crystals have been detected by measuring magnetic susceptibility in low (<50 Oe) magnetic fields. These regions produce a characteristic curve of (chi)(T,H) (symmetric in shape approaching a maximum value of similar to 10(-5) emu/g-enormous for this system) which is observed only at sufficiently low magnetic fields. Time and frequency dependencies of (chi)(T) along with x-ray diffraction data provide evidence in favor of a contribution from oxygen ordering to this effect. Crystals with differing excess oxygen content and mobility have been studied and the largest effect has been found in crystals with high oxygen mobility entering the superconducting state. [References: 21]