Internal stress and magnetic properties of electrodeposited amorphous Fe–P alloys

Abstract

Amorphous Fe–P alloys were electrodeposited under galvanostatic conditions at a current density of 10Adm–2 from sulfate–chlorine solutions containing β-alanine and glycine, as well as hypophosphoric acid. It was established that an increase in the deposition temperature from 50 to 60°C causes an increase in the deposition rate and a substantial rise in current efficiency and internal stress (IS). With pH increase from 2.0 to 3.0 the phosphorus content decreases, current efficiency almost doubles and there is a substantial drop in IS. It is assumed that a higher electrolyte acidity enhances hydrogen occlusion in the coating, which then desorbs from the deposit creating tensile IS. The same correlation between IS and current efficiency is observed when glycine concentration varies. A profile of residual IS is plotted illustrating the IS distribution throughout the deposit thickness. When the samples are magnetized in the coating plane, the shape of the hysteresis loop indicates perpendicular magnetic anisotropy. This is due to the columnar structure observed in scanning electron micrographs of the coating cross-sections. There is a linear dependence between IS and coercivity of amorphous Fe–P alloys deposited under different conditions.