Top panel: Growth rate σ_r/Ω in the (|Ro|,(N/Ω)²) of the SMRI, GSF and SH instabilities, for a regime typical of radiative regions (see Table 1, Λ_Z = 100, Λ_ϕ = 0). The three dashed lines correspond to instability thresholds, red for SMRI (Eq. (9)), blue for GSF, green for SH. The dotted lines separate the dominant type of instability inside the unstable domain from the mode properties. Bottom Panel: Stability map in the (k, α) plane for a stellar regime with |Ro| = 3 and Λ_Z = 100. Solid colored curves show the boundaries of the unstable domains for several values of the stratification parameter (N/Ω)². The blue region corresponds to the unstable range for (N/Ω)² = 10, and the star markers indicate, for each (N/Ω)², the most unstable mode (corresponding to the regimes indicated by the stars in the top panel). The black region denotes modes excluded by our assumptions. The densely dashed horizontal line indicates the upper limit of the GSF-unstable domain set by magnetic stresses. The dashed lines show the modified stability boundaries due to the combined action of magnetic stresses and stratification, shown here for (N/Ω)² = 5 × 10³ and 5 × 10⁵. The loosely dashed line marks the limit imposed by viscous diffusion. Labels indicate the domains of SMRI_‖, SMRI_⊥, and MGSF modes.