Magnetic domain structures and giant magnetoresistance of granular (Ni74Fe16Co10)(35)Ag-65 films

In this article, granular (NiFeCo)(35)Ag-65 films having a nominal atomic r atio of Ni:Fe:Co = 74:16:10, near the zero magnetostriction ternary alloy, were prepared by dc magnetron co-sputtering. Subsequent thermal annealing w as performed in a vacuum (< 2 x 10(-3) Pa) furnace for 1 h at various tempe ratures ranging from 250 to 500 degrees C. The crystalline structure and ma gnetic structure of the as-deposited and annealed films were characterized by Rutherford backscattering spectroscopy, x-ray diffraction, atomic force microscopy, and magnetic force microscopy. The giant magnetoresistance (GMR ) for the films was measured as a function of temperature between 20 and 30 0 K using a conventional four-point probe dc technique in the presence of a magnetic field up to 7.6 kOe. It was found that, the crystalline structure , the magnetic structure, and consequently the GMR were closely related to the thermal treatment. The film annealed at the temperature of 300 degrees C has the isolated single domain structure and the highest GMR value of 19. 1% at 20 K, while the film annealed at 500 degrees C has the long-range dom ain structure and the lowest GMR value of 9.9% at 20 K. (C) 2000 American I nstitute of Physics. [S0021-8979(00)04920-3].