Structure and properties of NiFe/NiFeO magnetic superlattice

Using a sequence of the sputtering deposition and the natural oxidation at low oxygen partial pressure, a thin (total thickness of 533-900 A) superlattice was produced consisting of NiFe18 and (NiFe18)O layers on Si, Si/SiO2, and GaAs substrates. The thickness of the as-deposited NiFe layers was in the range 9-533 A. It was found that the thickness of the NiFe film oxidizing as a result of the natural oxidation is limited to 10 A and produces about 16 A of the resulting NiFeO. It was determined that resistivity, saturation magnetization, magnetic anisotropy, and permeability could be controlled in the wide range of values by changing the thickness of the NiFe layers of the NiFe/NiFeO superlattice. Resistivity could be increased by up to two orders of magnitude and the Hk value could be increased by up to four times with respect to those of the NiFe18 film of a comparable thickness. Stress measurements were performed in a wide range of temperature to characterize the coefficient of thermal expansion and the biaxial modulus of the superlattice. Both values were found to be essentially identical to those of NiFe18 alloy. Thermal stability of the transport and magnetic properties of the NiFe/NiFeO superlattice with respect to 225 deg. C magnetic annealing was also determined