Submillimeter-wave ESR measurements of Ca(1-x)CuO2 (x=0.164) with edge-sharing CuO2 chains

Quasi-one-dimensional (1-D) cupric oxide Ca1-xCuO2 (x = 0.164) is the syste m with 25-40% hole-doped edge-sharing CuO2 chains. However, the holes are a lmost localized in Ca1-xCuO2 and its magnetic susceptibility with a peak at 30 K was explained by the model considering both L-D antiferromagnetic cha ins and spin dimers (Z. Hiroi, M. Okumura, Y. Nabeshima, T. Yamada, hi. Tak ano: J. Phys. Sec. Jpn. 69, 1824, 2000). To clarify the magnetic nature of Ca1-xCuO2, we performed submillimeter-wave electron spin resonance (ESR) me asurements on a powder sample of Ca0.83-6CuO2. The resonance above 12 K sho wed typical powder ESR of Cu2+ and the g-values were determined to be g(par allel to) = 2.33 and g(perpendicular to) = 2.06 from the analysis. The reso nance below 12 K changed completely from ESR. The frequency-field relation of ESR at 1.8 K clearly showed the easy-axis type antiferromagnetic resonan ce.