Complex antiferromagnetic order in the garnet Co3Al2Si3O12 (original) (raw)

We studied the magnetic properties of the garnet Co 3 Al 2 Si 3 O 12 synthesized under 5.5 GPa and 1250 °C by means of dc magnetic susceptibility, neutron powder diffraction, and specific heat. Although the magnetic Co 2+ ions form a geometrically frustrated hyper-Kagome lattice, we find that Co 3 Al 2 Si 3 O 12 exhibits a long-range antiferromagnetic order below T N = 11 K without showing magnetic frustration, i.e. the frustration index f ≡ |θ CW /T N | is close to unity. Refinements from neutron diffraction data show that Co 3 Al 2 Si 3 O 12 forms a complex antiferromagnetic structure characterized by the coexistence of collinear and commensurate spiral magnetic ordering of Co 2+ sublattices. Magnetic field induced spin-flop transition at μ 0 H c ≈ 4 T was also observed below T N .