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