Formation of unknown magnetic phase by solid state reaction of thin multilayered films of 75at%Mn-25at%Ge

Solid-state phase formation in Mn/Ge thin multilayered films with the compo sition of 75 at%Mn-25 at%Ge was investigated. The kappa-Mn5Ge2(LT) and zeta -Mn5Ge2(HT) phases were identified on annealing at 773 K. Although zeta-Mn5 Ge2 is known to be a high-temperature phase above 900 K, the formation of t his phase was confirmed on 773 K annealing. This may be due to non-equilibr ium thin film reaction process in multilayered films. Whereas on annealing at 973 K, the unknown magnetic phase with a tetragonal cell structure was f ormed. The lattice constant was determined to be a = 0.5174 and c = 1.580 n m by micro beam electron diffraction. The saturation magnetization of this phase is 2.4 emu/g at room temperature and 160 emu/g at low temperature (5 K), which is almost equal to the magnetization of ferromagnetic eta-Mn5Ge3. (C) 1999 Elsevier Science B.V. All rights reserved.