Gamow-Teller (GT) states excited by a charge-exchange reaction on N = Z nuclei with ground-state isospin T = 0 have isospin T = 1, while M1 states excited by inelastic scattering of electrons or protons can have either T = 0 or T = 1. The latter are the isobaric analog states of the GT states. By comparing the GT states observed in the good-resolution ( 3He, t) reaction at 150 MeV/ u with the M1 states observed in inelastic proton reactions, the isospin of each 1 + state in 28Si was determined. Furthermore, by comparing results from electron inelastic scattering induced by electro-magnetic M1 operator, different response of nucleus depending on different interaction is investigated. Based on these comparisons among different probes, we discuss (1) the contribution of the “ Δ- h excitation” mechanism in the quenching of magnetic excitations; (2) the effects of meson exchange currents; and (3) the orbital contribution in the M1 operator.