= Fe-Cr giant magnetoresistance experiments
{c}
{title2=1988–1989}
The 1988 study grew alternating <iron>/<chromium> layers by <molecular beam epitaxy> on <gallium arsenide>. <Magnetization> and <torque> measurements tested the magnetic configuration. An AC <electrical resistance> measurement passed <electric current> along the layers while the applied <magnetic field> changed. Comparing field directions and spacer thicknesses linked the resistance decrease to magnetic saturation. <Electron microscopy> and surface analysis checked layer formation, while leaving atomic-scale interface roughness unresolved.<Giant Magnetoresistance of (001)Fe⁄(001)Cr Magnetic Superlattices by Mário Norberto Baibich and others>[pp.2472–2474, preparation, Figs.1–3 and interface limits]{ref}
The independent Jülich study used <four-terminal sensing> on epitaxial Fe/Cr/Fe strips. A single <iron> film supplied an <anisotropic magnetoresistance> comparison. <Magneto-optic Kerr effect> signals and <Brillouin light scattering> from <spin waves> identified the layer alignments, rather than inferring them from resistance alone. Field scans along different magnetic axes connected the optical signatures to the resistance changes.<Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange by G. Binasch and others>[pp.4828–4830, four-point method, reference film and Figs.1–2]{ref}
<Peter Andreas Grünberg>'s retrospective explains why the preceding <interlayer exchange coupling> measurements mattered: coupled <spin wave> modes supplied signatures of magnetic alignment before that alignment became an electrical signal.<Nobel Lecture: From spin waves to giant magnetoresistance and beyond by Peter Andreas Grünberg>[pp.1533–1535, coupled modes and antiferromagnetic interlayer exchange]{ref}
\Image[/giant-magnetoresistance-in-plane-readout.png]
{title=Current along a magnetic multilayer and an independent check of layer alignment}
{description=Original functional illustration of current-in-plane transport and a generic four-terminal readout. Two idealized magnetic configurations are shown; dimensions, contact positions and layer count do not reconstruct either historical specimen. Optical probing supplies alignment information independently of the electrical signal.}
{source=giant-magnetoresistance-in-plane-readout.py}
A resistance curve alone does not reveal the microscopic direction of every magnetic layer. The optical measurements add a different observable, while the reference film tests an orientation-dependent response that can occur without a multilayer. Sample preparation and cross-checks therefore belong to the physical explanation.
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