The paper deals with viscoplasticity of ferromagnetic materials. Evolution equations are derived either from inelastic materials of differential type or from loading function generalized normality. In both cases tensor representation is applied to such a set of evolution equations. Restrictions to the set of field equations are established by means of the extended irreversible thermodynamics. Small magnetoelastic strains of isotropic insulators are considered in detail in two special cases of finite as well as small plastic strain. As one example low-cycle fatigue of ferromagnetics is considered with special account to time delay between stress and magnetic field histories. To describe such an experimental evidence an integro-differential equation is proposed whose equivalent plastic strain dependent kernel covers the observed delay.