Dipolar-Driven Mean-Field Criticality in the Ferrimagnet Eu_{2}MnSi_{2}O_{7}.

We report mean-field critical behavior in Eu_{2}MnSi_{2}O_{7}, a melilite-type ferrimagnet with spin-only Eu^{2+} and Mn^{2+} moments and negligible orbital contributions. Magnetization measurements combined with neutron powder diffraction reveal critical exponents close to the mean-field values, indicating that long-range dipolar interactions govern the asymptotic critical behavior in this insulating ferrimagnet. The refined magnetic structure, described by the magnetic space group P2_{1}2_{1}^{'}2^{'}, exhibits a tilted ferrimagnetic configuration driven by the Dzyaloshinskii-Moriya interaction, reflecting the noncentrosymmetric nature of the lattice. These results extend the applicability of mean-field theory to complex insulating magnets and establish Eu_{2}MnSi_{2}O_{7} as a platform for exploring ferrimagnetism and long-range interactions. To our knowledge, this is the first insulating ferrimagnet in which dipolar interactions drive mean-field criticality.