Comparison of the crystalline structure, morphology, and magnetic properties of γ -phase Mn Cu3 Au(100) ultrathin films by varying the growth temperature

The structural and magnetic properties of room-temperature (RT: 300 K) -grown and low-temperature (LT: 100 K) -grown Mn Cu3 Au(100) thin films were investigated. Mn films deposited at RT and LT demonstrate very different behaviors in the crystalline structure, morphology, and magnetism. RT-Mn films reveal apparent layer-by-layer growth for 0-2 ML (monolayer) followed by reduced oscillations. Although the medium-energy electron diffraction (MEED) oscillation is reduced, the intensity of specular spot increases monotonically after 6-7 ML, inferring the tendency of smooth morphology. The study of scanning tunneling microscopy also shows that even in 19 ML Mn Cu3 Au(100), the surface morphology is composed of large terraces with the size up to hundreds of nanometers. The LT-Mn films reveal apparent layer-by-layer growth for 0-5 ML followed by the reduced oscillations, and then the MEED intensity remains at low intensity, inferring the rough surface. The RT- and LT-Mn films exhibit a thickness-dependent structural transition from a face-centered cubic to a face-centered tetragonal structure at different critical thicknesses, ∼12-14 and ∼8 ML, respectively. Significant exchange bias is observed in Fe RT-Mn bilayers. It increases monotonously with Mn thickness. The exchange bias coupling in Fe LT-Mn is much weaker than Fe RT-Mn and drastically varies with Mn film thickness. The presence of exchange bias in the Fe Mn bilayers also indicates the antiferromagnetism of γ -phase Mn Cu3 Au(100).