Magnetic phase transition in the S= zigzag-chain compound SrCuO2

We have studied the magnetic properties of the S= quasi-one-dimensional Heisenberg antiferromagnet SrCuO2, which has zigzag chains of Cu2+ ions. We have observed a static magnetic ordering below Tc∼2 K. The weak internal field in the muon spin relaxation spectra and the absence of the magnetic Bragg peaks below Tc suggest that the Cu2+ moments are largely reduced probably due to the quantum fluctuation. The remarkable suppression of the ordering temperature (kTc/J2=1.1×10-3), where J2 is the dominant exchange constant, probably originates from the combined effects of quantum fluctuation and frustration.