Effect of the structural disorder on the magnetic, transport, and optical properties of B2-phase Ni0.50Al0.50 alloy films

The influence of structural disorder on the magnetic, transport, and optical properties of Ni0.50Al0.50 alloy films has been investigated. A significantly disordered state was obtained by using vapor-quenching deposition onto substrates cooled by liquid nitrogen. The loss of translational invariance in the disordered state leads to a prominent increase of the magnetic moment of alloy below 50 K. This growth can be explained by the appearance of antistructure Ni atoms (or their clusters) in the disordered state of alloy and their ferromagnetic coupling below 50 K. The temperature dependences of resistivity for both ordered and disordered states of the Ni0.50Al0.50 alloy films exhibit the resistivity minimum at 17-18 K, which has a nonmagnetic nature and can be related mainly to the quantum corrections to the electron-electron interactions in the presence of weak localization. It was shown that the resistivity of the ordered Ni0.50Al0.50 alloy films in 50-300 K temperature range originates mainly from the electron-phonon scattering, while in the disordered state the contribution from the electron-phonon-vibrating impurity scattering becomes dominant. The structural disordering also leads to a noticeable change in the optical properties of alloy, especially in the infrared region. The observed temperature and structural dependences of the resistivity as well as the optical properties in the intraband region confirm the thesis on partial localization of the electronic states near the Fermi level. (C) 2002 American Institute of Physics.