  A key phenomenon that enables nanoscale spintronic devices is the efficient
inter-conversion between spin and charge degrees of freedom. Here, we
experimentally demonstrate a pathway to generate current-induced spin
polarization at the interface between an insulating ferromagnet and a
non-magnetic metal using interfacial exchange-field spin filtering. Measuring
current-in-plane giant magnetoresistance in Py$|$Cu$|$EuS trilayer Hall cross
devices, we induce a non-equilibrium spin polarization of
$P_\text{neq}^\text{Cu|EuS}$=0.6% at a low charge current density of
1.88$\times$10$^3$ A/cm$^2$. This efficiency is comparable to that of
conventional charge-to-spin conversion of spin-Hall or Rashba-Edelstein effects
enabled by relativistic spin-orbit coupling. Interfacial exchange field
filtering allows operation with largely reduced power consumption and magnetic
reconfigurability, opening new pathways to nanoscale low-power insulator
spintronics.
