The disproportionation of \( \mathrm{MnO_4^{2-}} \) in acidic medium resulted in the formation of two manganese compounds A and B. If the oxidation state of Mn in B is smaller than that of A, then the spin-only magnetic moment \( (\mu) \) value of B in \( \text{BM} \) is _______. (Nearest integer)
