Abstract
CoPt and CoPtP thin films were synthesized using direct current (DC) aqueous electrodeposition from weak alkaline solutions. The basic plating solutions of binary CoPt thin films consisted of cobalt pyrophosphate [Co2P2O7] and chloroplatinic acid [H2PtCl6]. Various amounts of sodium hypophosphite [NaH2PO2] was added to deposit ternary CoPtP thin films. The film composition was adjusted by varying the several electrodeposition parameters including electrolyte composition, solution pH, and current density and correlated to their microstructure and magnetic property (i.e. coercivity and squareness). For the binary CoPt thin films, the maximum coercivities [in-plane coercivity (Hc,//) = ∼1,600 Oe, and perpendicular coercivity (Hc,⊥) = ∼2,500 Oe] were obtained from electrolytes containing 0.01 M H2PtCl6 + 0.04 M Co2P2O7 at current density (CD) of 7.5 mA cm−2. In the case of ternary CoPtP electrodeposits, the maximum coercivities (Hc,// = ∼2,600 Oe, and Hc,⊥ = ∼3,800 Oe) were achieved from baths containing 0.015 M H2PtCl6, 0.07 M Co2P2O7, 0.8 M NaH2PO2 at CD of 7.5 mA cm− 2 and solution pH 9. It was suggested that microstructure and magnetic properties are affected not only by the type of substrate but also by chemical compositions and electrodeposition conditions.
Highlights
CoPt and CoPtP alloys are promising hard magnetic materials due to their high magnetocrystalline anisotropy and magnetic saturation (Bozorth, 1963; Myung et al, 2003)
They investigated the effect of deposit time on current efficiency at different pH and different Co+2 ion concentration and reported the current efficiency of 55–68% and 55–78% with the change of deposit time, respectively
Magnetic CoPt and CoPtP thin film alloys were fabricated by electrodeposition process from the baths containing chloroplatinic acid, cobalt pyrophosphate and sodium hypophosphite
Summary
CoPt and CoPtP alloys are promising hard magnetic materials due to their high magnetocrystalline anisotropy and magnetic saturation (Bozorth, 1963; Myung et al, 2003). Despite the needs for integration of magnetic CoPt and CoPtP alloys by electrodeposition at near room temperature, limited works were carried out for electrodeposition baths and conditions. For binary CoPt thin films, the dependence of deposit contents, current efficiencies, and extrinsic magnetic properties (i.e., coercivity and squareness) on Co2+ ion concentration in plating baths was investigated. The optimum current density for the best coercivity of CoPt thin film was tested using the bath compositions and conditions of Table 1 with/without NaH2PO2 concentration (as P source). P content in the CoPtP thin films could not be analyzed using both AAS and energy dispersive spectroscopy (EDS) because of interference between Pt and P elements Magnetic properties such as coercivity (HC) and squareness (S Mr/MS) were measured
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