Magnetoresistance ofSmMn2Ge2: A layered antiferromagnet

The behavior of the magnetoresistance in ${\mathrm{SmMn}}_2$ ${\mathrm{Ge}}_2$–a layered intermetallic compound–is analogous to the giant magnetoresistance recently reported for artificial metallic multilayers. A moderate magnetic field (2–15 kOe) is sufficient to switch ${\mathrm{SmMn}}_2$ ${\mathrm{Ge}}_2$ from the antiferromagnetic (metamagnetic) state to saturation, at a temperature of ∼100 K, and this results in a resistance change of 4–8 %. The study of spin-dependent scattering in this and similar layered structures, in which nature has conspired to make essentially perfect interfaces, serves as a complement to the study of the artificial structures.