2-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET WITH EXTRA-SPIN-INDUCED FRUSTRATION

A square lattice Heisenberg antiferromagnet with extra-spin-induced frustration is studied by means of spin wave theory. The extra spins are inserted between every two adjacent host spins on the square lattice. The interaction between host spins and extra spins causes the system to be frustrated. We find that for a wide range of frustration parameter the classical ground state is heavily degenerate and an ordered state is no longer stable, regardless of the magnitude of spins. This fact suggests the existence of spin-liquid ground state in the range. We also find that the Neel order of square lattice antiferromagnet can be destroyed with only a little frustration introduced in this model.