Effect of Two-Step Annealing on Remanence of Fe-Pt Films Electroplated on Cu Substrates

We have already reported a fabrication method of Fe-Pt thick film magnets using electroplating and good film’s hard magnetic properties. The present study investigates two-step-annealing, consisting of low- temperature annealing (LT-annealing, 300°C) and high-temperature one (HT-annealing, 700°C) for ordering the Fe-Pt crystalline phase. We electroplated Fe-Pt films on a Cu sheet and carried out the two-step-annealing for the films. As a result, the remanence of the two-step-annealed Fe-Pt films varied depending on the holding time of the LT-annealing, and we obtained a high remanence at the holding time of around 10 min. As a next step, we annealed the Cu sheets at 300°C and electroplated Fe-Pt films on the 300°C-annealed Cu sheets. In this case, no noticeable variation in remanence was observed. As the structural change of the Cu sheet by the 300°C-annealing was confirmed using X-ray analysis, the structural change of the Cu substrate is a factor for the remanence variation by the LT-annealing. In other words, we found that the remanence can be controlled by using the structural changes of the Cu substrate.