  Based on a simple model for spin-polarized scanning tunneling spectroscopy
(SP-STS) we study how tip magnetization and electronic structure affects the
differential conductance (dI/dV) tunneling spectrum of an Fe(001) surface. We
take into account energy dependence of the vacuum decay of electron states, and
tip electronic structure either using an ideal model or based on ab initio
electronic structure calculation. In the STS approach, topographic and magnetic
contributions to dI/dV can clearly be distinguished and analyzed separately.
Our results suggest that the sensitivity of STS on a magnetic sample can be
tuned and even enhanced by choosing the appropriate magnetic tip and bias
setpoint, and the effect is governed by the effective spin-polarization.
