Electromagnetic fundamental physical constant: \[\mu _{\text{B}} = \frac{e\ \mathrm{\hslash }}{2\ m_{\text{e}}} = 9.274\hspace{0.5em}0154\hspace{0.25em}\left(31\right)\times 10^{-24}\ \mathrm{J}\ \mathrm{T}^{-1}\] where e is the elementary charge, ℏ the Planck constant divided by 2π and m e the electron rest mass.