  We probe the quantum speed limit (QSL) of an electron when it is trapped in a
non-uniform magnetic field. We show that the QSL increases to a large value,
but within the regime of causality, by choosing a proper variation in magnetic
fields. We also probe the dependence of QSL on spin of electron and find that
it is higher for spin-down electron in the relativistic regime. This can be
useful in achieving a faster speed of transmission of quantum information.
Further, we use the Bremermann--Bekenstein bound to find a critical magnetic
field that bridges the gap between non-relativistic and relativistic treatments
and relates to the stability of matter. An analytical framework is developed.
We also provide a plausible experimental design to supplement our theory.
