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Y-type hexaferrite Ba₂Mg₂Fe₁₂O₂₂ is a promising multiferroics that is sensitive to small magnetic field. When doped with Sr, the material keeps its sensitivity to field while the ME coefficients are greatly enhanced with Sr level increasing. Our recent work has reported new records of ME coefficients in single phase materials at Ba_0.4Sr_1.6Mg₂Fe₁₂O₂₂. With neutron scattering study, we found that there is a link between the ground state spin cone symmetry and the magnitude of the polarization which could be modulated sufficiently with Sr doping level. Temperature dependent neutron diffraction investigation shows pinning effect emerging at heavy Sr doped sample that has an alternating longitudinal conical ground state. The study of size effect indicates that the simultaneously occurred effects could correspond to relatively independent mechanisms.