Influence of Cu(100) Substrate on Growth, Morphology, Structural and Magnetic Properties of High Coercivity Electrodeposited Co-Pt-P Thin Films

Abstract

Co-Pt-P ͑ϳ20 atom % Pt, ϳ3 atom % P͒ alloy films with thickness from 125 to 1000 nm have been grown by electrodeposition under constant current on a ͑100͒ oriented Cu seed layer. The influence of deposition current density and film thickness on their chemical composition, growth morphology, and structural and magnetic properties have been investigated. Co-Pt-P films consist of a fcc phase with ͑100͒ and ͑111͒ preferential orientations and a variable amount of hcp phase with ͑00.2͒ orientation, which increases with increasing current density. Grain size decreases with increasing current density. At high current density, the films exhibit significant perpendicular anisotropy and hard magnetic properties in the out-of-plane direction, with coercivity up to 3.7 kOe ͑295 kA/m͒.

Electrodeposition of hard magnetic films and microstructures

“…Deposition was carried out at a sputtering power density of 7.96 W/cm 2 using Ar as the sputtering gas at a pressure of 10 or 0.4 mTorr, respectively. These Cu layers grow epitaxially on Si, as confirmed by X-ray diffraction (XRD) pole figure measurements [6,7]. Cr seed layers were sputter coated on either glass slides or Si(0 0 1) substrates with the native oxide layer [8].…”

“…About 3 at.% each of O and P were detected by XPS; these elements might have been incorporated due to metal hydroxide precipitation and as a consequence of side reactions of the hypophosphite anions. Film composition was uniform along its thickness [7].…”

“…We further find that their relative fraction can be controlled by current density. TEM diffraction in fact shows that at high CD the volume fraction of the hcp phase increases, and in addition the grain size decreases [7]. The Cu(1 1 1) substrate favors growth of these close-packed orientations right from the substrate, due to a correct symmetry of the surface atomic structure and a good lattice matching.…”

Structural influence of copper substrate on magnetic properties of electrodeposited CoPtP films for MEMS applications

“…The seed layer consisted of 100 nm of Cu film thermally evaporated on the glass substrate under the vacuum pressure of 10-5 mbar. These copper layers grow epitaxial on Si, as confirmed by X-ray diffraction (XRD) pole figure measurement [10,11]. This layer structure of Cu substrate is strongly oriented with the multilayer electrodeposition of CoPtP alloy.…”

Current Density and Thickness Effects on Magnetic Properties of Electrodeposited CoPt Magnetic Films

“…Therefore, the main magnetic interaction is the dipolar interaction, as shown in the 10 mA/cm 2 samples [12]. According to I. Zana et al [18], the non-magnetic phases P (or P compounds) were precipitated at the grain boundaries while electrodepositing. Therefore, the dipolar interaction in our samples may be resulted in these non-magnetic phases.…”