Direct observation of pinned/biased moments in magnetic superlattices

We report the \QTR{it}{pinned/biased} \QTR{it}{moment} in the superlattices consisting of ferromagnetic (FM) SrRuO$_3$ and antiferromgnetic (AFM) SrMnO$_3$. This superlattice system shows anisotropy and oriented pinning/biasing in the field-cooled (FC) hysteresis loop. The in-plane cooling-field provides antiferromagnetic orientations while out-of-plane cooling-field provides ferromagnetic orientations to the pinned/biased moments. The spacer layer thickness, strength and orientation of magnetic field, cooling field, and driving current influence the pinning strength. We propose that the magnetic structure is a repetition of $AFM/Pin/FM$($Free$)/$Pin$ unit below a critical field to explain its magnetic and transport properties. The transport behavior is discussed using the spin-dependent conduction.