[en] Single crystals of Tb-Tm alloys, Nd and MnSi were investigated by neutron diffractometry. Four Tb-Tm alloys were investigated in the temperature range of 4.2-300 K, all ordering magnetically to a basal plane spiral below the Neel temperature but with different orders below the Curie temperature. The study showed unambiguously that Tb-Tm alloys have an inhomogeneous phase, where the spins associated with the Tb ions lie in the basal plane, while the spins associated with the Tm-ions order along the c-axis. The magnetic structure of Nd was investigated between 4.2 K and the ordering temperature 20 K. It is shown that the magnetic structure can be understood with the assumption of single ion anisotropy and that the critical exponent is in agreement with the epsilon-expansion. MnSi is shown to be an example of a magnetic material of nearly itinerant character. The magnetic structure is a spiral one below the ordering temperature (26.7 K). In a magnetic field the structure transforms into a cone structure at 1 kGauss and above 6 kGauss it is ferromagnetic. (Auth.)