Control of magnetic properties of Invar alloy by using giant stress in thin films.

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Atomic magnetic moment depends on the atomic distance and/or crystalstructure. Based on this view point, the Fe-Ni alloy sputtered thin films have been investigated.As-deposited films on the glass substrates show the saturated magnetization expected from ideal alloy. The structure is, however, amorphous structure. After annealing, the structure changes into polycrystalline and saturation magnetization decreases. To obtain the f.c.c. crystalline phase in as-deposited state, Au under layr is adopted. Then, the f.c.c.phase is realized in a concentration range over the 30at%Ni. Based on this result, the Fe_<0.7>Ni_<0.3> films on the Au under layr are investigated. The atomic magnetic moment depends on the film thickness of Fe_<0.7>Ni_<0.3>. in a range less than 60nm. The crystal deformation is evaluated by using x-ray diffraction and transmission electron diffraction. Fe_<0.7>Ni_<0.3>/Au show the lattice deformation toward surface normal.On the other hand, to induce further lattice deformation on the Fe_<0.7>Ni_<0.3> films on Au under layrs, stacking of sputtered Mo layrs are examined. It is confirmed that the internal film stress of the Mo can be changed with working Ar gas pressure. In the case of Mo/Fe_<0.7>Ni_<0.3>/Au stacking structure, the lattice deformation takes place in both directions of the in-plane and surface normal direction.As the result, in the film of Fe_<0.7>Ni_<0.3> anisometric lattice deformation was observed by the stacking of Mo and/or Au layr. The corresponding atomic magnetic moment changes with the averaged lattice parameter. The trajectory of the change, however, depends on the lattice deformation.