Usually it is believed that the Hartree-Fock state of quark matter is a Fermi
gas state with no polarisation of spins. We examine the possibility of the
polarised quark liquid interacting with the one-gluon-exchange interaction. It
is suggested that the Hartree-Fock state shows a spontaneous magnetic
instability at low densities through the same mechanism as the appearance of
ferromagnetism in electron gas. Metastability of the polarised quark liquid is
also discussed.Comment: 14 pages, 2 postscript figure
