Electroplated thick-film cobalt platinum permanent magnets

The material and magnetic properties of multi-micron-thick (up to 6 μm) L1₀ CoPt magnetic films electroplated onto silicon substrates are investigated as candidate materials for integration in silicon-based microsystems. The influence of various process conditions on the structure and magnetic properties of electroplated CoPt thick-films is studied in order to better understand the complex process/structure/property relationships associated with the electroplated films. Process variables studied here include different seed layers, electroplating current densities (ranging from 25–200 mA/cm²), deposition times (up to 60 min), and post-deposition annealing times and temperatures. Analyses include film morphology, film thickness, composition, surface roughness, grain size, phase volume fractions, and L1₀ ordering parameter. Key correlations are found relating process and structure variations to the extrinsic magnetic properties (remanence, coercivity, squareness, and energy product). Strong hard magnetic properties (B_r ~0.8 T, H_ci~800 kA/m, squareness close to 0.9, and BH_max of 100 kJ/m³) are obtained for films deposited on Si/TiN/Ti/Cu at current densities of 100 mA/cm², pH of 7, and subsequently annealed at 675 °C for 30 min.