Direct Observation of Localized Spin Antiferromagnetic Transition in PdCrO(2) by Angle-Resolved Photoemission Spectroscopy

We report the first case of the successful measurements of a localized spin antiferromagnetic transition in delafossite-type PdCrO(2) by angle-resolved photoemission spectroscopy (ARPES). This demonstrates how to circumvent the shortcomings of ARPES for investigation of magnetism involved with localized spins in limited size of two-dimensional crystals or multi-layer thin films that neutron scattering can hardly study due to lack of bulk compared to surface. Also, our observations give direct evidence for the spin ordering pattern of Cr(3+) ions in PdCrO(2) suggested by neutron diffraction and quantum oscillation measurements, and provide a strong constraint that has to be satisfied by a microscopic mechanism for the unconventional anomalous Hall effect recently reported in this system.