Magnetic Correlations in La_2-xSr_xCoO₄ Studied by Neutron Scattering: Possible Evidence for Stripe Phases

Spin correlations in La_2-xSr_xCoO₄ (0.3≤x≤0.6) have been studied by neutron scattering. The commensurate antiferromagnetic order of La₂CoO₄ persists in a very short range up to a Sr content of x=0.3, whereas small amounts of Sr suppress commensurate antiferromagnetism in cuprates and in nickelates. La_2-xSr_xCoO₄ with x>0.3 exhibits incommensurate spin ordering with the modulation closely following the amount of doping. These incommensurate phases strongly resemble the stripe phases observed in cuprates and nickelates, but incommensurate magnetic ordering appears only at larger Sr content in the cobaltates due to a reduced charge mobility.