Magnetic properties of doped kagomé antiferromagnet

In order to clarify the carrier doping effect in the frustrated system, we study the t - J model on the kagomé lattice using high-temperature expansion method. As in the triangular lattice [T. Koretsune, M. Ogata, Phys. Rev. Lett. 89 (2002) 116401], the sign of hopping integral t is important in the kagomé lattice. When t < 0, the possibility of ferromagnetism has been discussed [T. Koretsune, M. Ogata, J. Phys. Soc. Japan 72 (2003) 2437]. On the contrary, in the case of t > 0, it is found that uniform spin susceptibility is strongly suppressed with hole doping. The peak of spin susceptibility, which is expected to be around T = J / 20 in the Heisenberg model, goes to high temperature region. Furthermore, short-range magnetic correlation is enhanced with hole doping. This is interesting since nearest-neighbor spin correlation without hole doping itself is strongly enhanced by quantum fluctuation. These behavior are qualitatively similar to those of the triangular lattice. However, the difference from non-frustrated lattices as square lattice is more prominent in the kagomé lattice, which is related to the fact that frustration in the kagomé lattice is strong enough to destabilize the magnetic order in the Heisenberg model even at T = 0.