Magnetic, structural and magnetoresistive properties of magnetron-sputtered thin NiFe films

Abstract

The resistivity, magnetoresistance ratio, magnetic hysteresis loop and structure of magnetron-sputtered permalloy (Ni81Fe19) films of thickness 200-1600 Å were studied and compared with the corresponding properties of permalloy films prepared by electron beam evaporation. The r.f.-sputtered films were prepared in an argon plasma from a sputter gun with an aligning magnetic field of 400 Oe applied in the plane of the substrates. No external heating or substrate bias voltage was used during the deposition. The resistivities of sputtered permalloy films show a similar thickness dependence to that for evaporated films, although with higher values. The residual resistances of the sputtered films are also higher; this is attributed to the greater amount of incorporated gases and possibly less atomic ordering. From the thickness dependence of the resistivity as measured in the range 200-1600 Å, the value of the boundary reflection coefficient was estimated and was found to be almost the same as that reported earlier for permalloy films deposited in an ultrahigh vacuum. X-ray diffraction techniques were employed to measure the intrinsic isotropic stress σ which was found to be about 6×109 dyn cm-2. The magnetoresistance ratio of the sputtered films is less than 2%, which might be explained by their higher resistivity values. The coercivity of the films is in the range 1.5-3 Oe, which is higher than that of evaporated permalloy films. The same was true of the anisotropy field, which is between 5 and 6.5 Oe. © 1985.