Theoretical investigation of the magnetic spiral behavior in a layered magnet with strong hexagonal magnetic anisotropy has been performed. It is shown that if the exchange integrals between the first and second neighboring layers meet the requirement jJ 1 j ¼ ÀJ 2 , the energy densities for spirals with three and four (at J 1 < 0) or four and six (at J 1 > 0) layers in the period coincide. Moreover, near the surface of contact of the above phases the energy density is equal to or even lower than inside each of them, which should result in the appearance of a domain magnetic structure.ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Materials in which alteration of magnetic structure accompanied by changes in conductivity, electrical polarization, optical properties, etc., arises upon small variations in some external parameters are attractive for practical applications. The processes of such type can take place either if a new magnetic phase appears in the course of a first-order transition or if a domain magnetic structure with easily moveable boundaries exists in the system. In particular, it would seem promising to produce domain structure in a layered magnet, i.e., natural or artificial crystal or film consisting of atomic layers with ferromagnetic ordering of magnetic moments inside them. In such structure, magnetic spirals could form, and if the energy densities for helicoids with different periods are close to each other, these helicoids would form stratified ''domain structure.'' In this case, magnetic scattering of particles with the wavelength of the order of interlayer distance could be controlled by changing the relative volumes of helicoids. The recent studies of complex magnets consisting of pairs of not identical magnetic layers give us some grounds to suppose that strongly different magnetic spirals could actually coexist.The above studies deal with a considerable number of compounds in which magnetic layers are separated by alternating unequal spacings filled with different nonmagnetic atoms, and the type of spin ordering is identified as a double nested magnetic spiral.