In the beginning of 2008 a large number of papers are published devoted to materials based on FeAs. In these materials the superconducting transition temperature are up to 56 K [1]. The characteristic of these materials is a multi-zone and layered structure. These features play a crucial role in phase transitions, including magnetic and superconducting transitions. In this paper, we restrict ourselves to the study of magnetic states, without studying their superconductivity. New high-temperature systems based on FeAs have a lot of different basic magnetic states, divided in two great classes: ferropnicttides and ferrochalcogenides. As the basis of the model on magnetism, we may put normal interaction of localized moments. Along with this new material there is also present the magnetic state associated with the spin density wave, thanks to the "nesting" on the Fermi surface and the adjustment of the electron energy spectrum. In this paper, a theory is developed of the thermodynamic properties of the SDW in quasi-state system with deviation from half filling of energy band (given by the impurity concentration x). The anisotropic law of energy dispersion of the electrons has been selected, and included the magnetic field has an arbitrary direction relative to the magnetic moment . It is shown the system of equations obtained by Hubbard Hamiltonian. The parameters of the order and , the conversion of this system is done, taking into account the transfer of processes. Special cases are examined in detail: and , and cases of small magnetic fields of arbitrary direction. We analyze the condition of a system transition in the commensurate and incommensurate SDW state. In the last case, due to the conditions of the incommensurability of the dielectric gap is displaced to the Fermi surface, which contributes to the emergence of free carriers and the formation of the metallic state. In turn, it can lead to superconductivity in the background of the GSP. We calculate the dependence of the magnetic transition temperature TM and we identify the components of the order parameter of the incommensurate phase. The phase diagram . The influence of magnetic field on TM in the cases , and also the longitudinal magnetic susceptibility χ | | is known, which shows when the temperature behavior is similar to the presence of cracks in the system, and when - gapless state. In the immediate vicinity of the critical impurity concentration , where the incommensurate SDW state is formed, depending on χ | | by T / TM found a local maximum. Also is analyzed the effect of anisotropy on the energy spectrum studied in the physical quantities. [1] Xiyu Zhu, Huong Vang, Lu Fang at al., Superconduc. Sci. Tehnol., 21, 105001 (2008).