  The inversion of a spin valve device is proposed. Opposite to a conventional
spin valve of a non-magnetic spacer sandwiched between two ferromagnetic
metals, an inverse spin valve is a ferromagnet sandwiched between two
non-magnetic metals. It is predicted that, under a bias, the chemical
potentials of spin-up and spin-down electrons in the metals split at
metal-ferromagnet interfaces, a dynamical Zeeman effect. This split is of the
order of an applied bias. Thus, there should be no problem of generating an
$eV$ split that is not possible to be realized on the earth by the usual Zeeman
effect.
