Fine tuning of coercivity in electrodeposited, Co-rich Co-Pt alloy films with perpendicular orientation

We study the effect of applied current density j on the magnetic properties of Co-rich Co-Pt electrodeposited onto Ru (0001) Cu (111) Si (011). We find that varying j in the range of 10-100 mA cm2 has a limited influence on film composition but has a strong effect on coercivity Hc. For example, Hc increases from 1600 to 4700 Oe in 100 nm thick Co-Pt films simply by increasing current density, providing an easily accessible parameter for the direct tuning of film coercivity. A higher current density increases nucleation density and consequently reduces grain size. It is hypothesized that the increased rate of side reactions at high j induces an increase in interface pH, affecting the hydrolysis equilibria in the electrolyte and leading to a variable incorporation of nonmagnetic matter that preferentially segregates at grain boundaries.