Parameters are presented for a metastable crystal of an alkali metal which is composed of atoms with unidirectionally aligned spins, such as the distance between nearest neighbors, the sublimation energy, the Debye temperature, the change of energy accompanying spin reversal, the rate of evaporation of atoms from a surface, etc. The distance between nearest neighbors in the crystals under consideration considerably exceeds atomic dimensions, so that these ferromagnetic crystals are dielectrics. Analysis shows that they can be actually produced at a low temperature of the order of a few degrees Kelvin.