Development of nanostructured, stress-free Co-rich CoPtP films for magnetic microelectromechanical system applications

Abstract

Co-rich CoPtP alloys have been electrodeposited using direct current (dc) and pulse-reverse (PR) plating techniques. The surface morphology, crystalline structure, grain size, and magnetic properties of the plated films have been compared. The x-ray analysis and magnetic measurements reveal the presence of Co hcp hard magnetic phase with c axis perpendicular to the substrate for dc and in plane for PR plated films. The dc plated films have a granular structure in the micron scale with large cracks, which are manifestation of stress in the film. Only by using a combination of optimized PR plating conditions and stress relieving additive, we are able to produce 1–6μm thick (for 1 hour of plating), stress-free, and nanostructured (∼20nm) Co-rich CoPtP single hcp phase at room temperature, with an intrinsic coercivity of 1500Oe.

Stability of the electrodeposition process for CoPt alloy formation

“…During the following years, the films were studied mainly in terms of their thickness, structure and magnetic properties. The importance of epitaxial growth, substrate material and its structure for the deposition of films with high magnetic parameters was shown by Zangari, Cavallotti et al [7][8][9][10][11][12][13][14][15][16][17][18]. The results of these investigations pointed to the great potential of electrodeposition for manufacturing CoPt and CoPtP permanent magnet films.…”

“…Among several possible electrodeposited alloys, CoPt alloys are the most promising, as annealed equiatomic alloys possess very high magnetic parameters [3][4][5]. Furthermore, as-deposited CoPtP alloys exhibit magnetic properties acceptable for some applications [6][7][8][9][10][11][12][13][14][15][16][17][18][19] where high temperature annealing is forbidden or limited. These CoPt and CoPtP alloys can be deposited with current efficiencies and deposition rates up to 20% and 12 lm/h, respectively, from citrate electrolytes containing [Pt(NO 2 ) 2 (NH 3 ) 2 ] 0 as the source of Pt.…”

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

“…The electrolyte was used for depositing films using DC plating at current densities varying from 2.5 to 20 mA/cm 2 at room temperature for various time of deposition from 15 to 60 min. The current density varying from 15 to 20 mA/cm 2 for 1 h deposition films thickness were above 1 lm [13]. So the below 10 mA/cm 2 current densities ware varied to get optimized structure and magnetic properties of the film.…”

Ternary CoPtP electrodeposition process: Structural and magnetic properties of the deposits

“…Different Co alloys have been prepared by electrodeposition for this purpose [8] and even electrodeposition through lithographically defined masks is sometimes used [9]. Some CoPt and CoPtP alloys seem to be promising candidates due to their good hard magnetic properties [10][11][12][13][14][15][16]. Although some authors describe how CoPt films with optimum hard magnetic properties can be prepared by electrodeposition, few studies deal with the electrochemical behaviour of the binary or ternary electrodeposition process [17].…”