Effects of doping on spin correlations in the periodic Anderson model

We studied the effects of hole doping on spin correlations in the periodic Anderson model, mainly at the full and three-quarters-full lower bands cases. In the full lower band case, strong anti-ferromagnetic correlations develop when the on-site repulsive interaction strength $U$ becomes comparable to the quasi-particle band width. In the three-quarters full case, a novel kind of spin correlation develops that is consistent with the resonance between a $(\pi,0)$ and a $(0,\pi)$ spin-density wave. In this state the spins on different sublattices appear uncorrelated. Hole doping away from the completely full case rapidly destroys the long-range anti-ferromagnetic correlations, in a manner reminiscent of the destruction of anti-ferromagnetism in the Hubbard model. In contrast to the Hubbard model, the doping does not shift the peak in the magnetic structure factor from the $(\pi,\pi)$ position. At dopings intermediate to the full and three-quarters full cases, only weak spin correlations exist.