Abstract
A new type of colossal magnetoresistance, which is extremely sensitive to the magnetic-field direction, was discovered in a magnetoplumbite-type hexagonal cobalt oxide SrCoO synthesized under a high pressure of 3 GPa. SrCoO has a unique combination of physical properties (i.e., uniaxial magnetic anisotropy originating from Ising spins on CoO bipyramids and a metal-insulator transition taking place on a three-dimensional network of CoO octahedra). The resistivity decreases by a factor of 1000 when a magnetic field of 10 T is applied along the hexagonal axis (magnetic easy axis) in the insulating phase, whereas it is rather robust against the field perpendicular to this axis. These results demonstrate a metal-insulator crossover dominated by the orientation order of built-in Co Ising spins embedded in the conductive Co-O matrix lattice.
- Received 27 September 2010
DOI:https://doi.org/10.1103/PhysRevB.83.020401
© 2011 American Physical Society