Effect of structural disorder on the physical properties and electronic structure of the DC magnetron sputtered Ni films

摘要

The effect of the structural disorder in Ni films on their magnetic, magneto-optical (MO), transport, optical properties, and the spin polarization degree of conduction electrons as well as the electronic structure has been investigated. Room temperature (RT) DC magnetron sputtered onto glass substrates Ni films have been found to be amorphous. It was experimentally shown that an amorphous Ni films (ⅰ) are not ferromagnetically ordered at least for T ＞ 78 K temperature range, (ⅱ) do not show any MO response at RT, (ⅲ) have 10 times larger resistivity than crystalline phase which nearly does not depend on temperature, (ⅳ) exhibit the optical conductivity (OC) spectrum without interband absorption peaks typical for crystalline Ni, (ⅴ) have spin polarization degree of conduction electrons close to zero. Annealing of amorphous Ni films at T = 600 K causes their crystallization with the formation of the face-centered-cubic phase and restores the physical properties typical for crystalline Ni. The experimental OC spectrum of crystalline Ni film exhibits an intense interband absorption peaks located at E = 1.4 and 4.55 eV; it is in reasonable correspondence with the calculated interband OC spectrum of Ni. Main absorption peaks in the experimental OC spectrum were put in correspondence with the electron excitations between definite electronic states of the E(k) structure of Ni. The experimentally determined spin polarization degree of conduction electrons of crystalline Ni films was found to be close to that for bulk Ni and consists of P ≈ 40%.