Spiral spin states in a generalized Kondo lattice model with classical localized spins

A generalized Kondo lattice model with classical localized spins is studied in a two-dimensional case. Our model includes the case in which antiferromagnetic exchange coupling J exists between localized spins. We obtain the magnetic phase diagram on the plane of J and fermion concentration n, and the order of each phase transition on the phase diagram, taking into account all possible planar spiral orders and canted ferromagnetic orders as well as the Néel order and the ordinary ferromagnetic order. In the phase diagram, we find a large region of the stripe spiral phase, which is consistent with the results of neutron-scattering experiments of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$.