Electric and magnetic anomaly in single crystalline CuO

A 150 K anomaly is observed in the electric resistivity of vapor-grown sing le crystalline CuO. The single crystal is semiconductive with an activation energy of 0.11 eV, whereas the single crystal annealed in oxygen atmospher e shows an anonymous shoulder feature on the resistivity-temperature curve around 150 K. DC magnetization measurement shows that the resistivity anoma ly is accompanied by a change in the anisotropy of susceptibility, suggesti ng a relation to magnetic structure. This result is interesting, particular ly when viewed in the light of strong correlation in copper oxides. (C) 199 9 Elsevier Science B.V. All rights reserved.