Structural, magnetic, and electron transport properties of MnBi:Fe thin films

The structural, magnetic, and electron transport properties of Mn55-xFexBi45 (x = 0, 2, 4, 5, 8, 11, 13, 16) films prepared by multilayer deposition and annealing using e-beam evaporation have been investigated. Fe doping has produced a significant change in the magnetic properties of the samples including the decrease in saturation magnetization and magnetocrystalline anisotropy and increase in coercivity. Although the magnetization shows a smooth decrease with increasing Fe concentration, the coercivity jumps abruptly from 8.5 kOe to 22 kOe as Fe content changes from 4% to 5%, but the change in coercivity is small as the concentration goes beyond 5%. The temperature dependence of resistivity shows that the samples with low Fe concentration (<= 4%) are metallic, but the resistivity increases unexpectedly as the concentration reaches 5%, where the resistance increases with decreasing temperature below 300 K. First-principle calculations suggest that the observed magnetic properties can be understood as the consequences of competing ferromagnetic and antiferromagnetic exchange interactions between the interstitial atom and the rest of the MnBi lattice. (C) 2012 American Institute of Physics. [doi:10.1063/1.3675615]