Shutylieva O. The phase composition, magnetoresistive and magnetic properties of devices structures based on Ni and Co and Dy or Bi

The PhD thesis is devoted to a complex study of the influence of the structural-phase state on the magnetic and magnetoresistive properties of devices structure based on film systems of transition ferromagnetic (Ni or Co) metals and rare earth Dy or Bi and to establish the influence of sample orientation in an external magnetic field. The interconnection between the features of the structural-phase state of the structures of devices in the form of three-layer film systems and their magnetic and magnetoresistive properties has been established. The phase composition of three-layer films based on Co and Bi in the as-deposited state corresponds to hcp-Co, fcc-Co, and rhombohedral-Bi. Three-layer films based on Ni or Co and Dy (dDy < 15 nm) before and after heat treatment, the phase composition is as follows: fcc-Ni + qa-Dy and hcp-Co + fcc-Co + qa-Dy. It is established that for all investigated film systems the anisotropic character of the magnetoresistance at room temperature of measurement is fixed. The maximum MR values for systems based on Ni or Co and Dy are observed in the perpendicular measurement geometry when Dy is in the quasi amorphous state. For a system based on Co and Bi, the maximum values are observed at its largest thicknesses in the system in the perpendicular geometry of the measurement. When the thickness of the layer changes from qa-Dy, the dependence of the magnetoresistance and coercive force reveals a nonmonotonic character, which disappears during the layer Dy transition to the crystalline state. Studies of magnetic properties have shown that after heat treatment in three-layer films in most cases there is an increase in the value of coercive force, saturation magnetization, and residual magnetization. In three-layer Co/Bi/Co films in an as-deposited state, the coercivity does not depend on the thickness of the Bi layer and after annealing to 680 K, its value increases with increasing effective Bi thickness. The possibility of practical use of research results for the development of functional elements of induction position sensors, anisotropic magnetoresistive position, and angle sensors, magnetic medium of information recording, which will have stable operating characteristics in a wide temperature range, is shown