Structural and magnetic properties of sputtered NiFe films grown in a dc discharge environment

Abstract

Experimental evidence is presented which verifies Middlehoek's recent extension of the Néel theory relating the coercivity with film thickness variations. Under special preparatory conditions "inverted" NiFe films on glass substrates were produced with excellent reproducibility. Partial oxidation leading to antiferromagnetic inclusions was shown to be absent. Resolution of the substrate temperature control problems using metal substrates in the plasma environment enabled us to show that a uniaxial anisotropy can only be induced into sputtered NiFe films over a limited temperature region. Temperature control during film growth also made possible a direct correlation of film morphology with the magnitude and uniformity of the dispersion of the easy axis of magnetization and the resultant critical field for wall motion Hc. Typical coercivity Hc, anisotropy field strength HK, and dispersion measurements on 700-Å NiFe films on very smooth 25 cm2 Ag: Cu-SiO substrates were: Hc=1. 92±0.07 Oe, HK=2.85±0.03 Oe, dispersion=1.0±0. 0°. Special problems pertaining to film growth in a plasma environment are discussed. A typical Lorentz micrograph of a sputtered NiFe film deposited directly onto a microscope grid is given. © 1964 The American Institute of Physics.