Novel epitaxial growth and magnetotransport characterization of single crystal Co(1120)Cr(100) superlattices on Mo buffer layers

Single-crystal Co(1120)Cr(100) superlattices (SLs) have been successfully grown on MgO (100) and Al2O3 (1102) substrates with 100 Å Mo as buffer layers by molecular beam epitaxy (MBE). Excellent epitaxial growth was evidenced by reflection high-energy electron diffraction (RHEED). Magneto-resistance (MR) measurements have been performed using a conventional four-point technique. We have observed negative MR (NMR ≈ 4.8%) for [Co(40 Å)Cr(5 Å)]70 SLs, giant positive MR (PMR ≈ 30%) for [Co(5Co)Cr(5 Å)]100 SLs. It is likely that the NMR effect is introduced by the CoCr SL while PMR is induced by the Mo buffer layers. Interestingly, PMR samples show a distinct roughness effect compared to NMR samples. Systematically we have found that NMR increases with increasing interfacial roughness, while PMR samples show the opposite behavior.