Influence of temperature on the magnetic properties of electroplated Co-rich Co–Pt thick films

In this paper, the magnetic properties of 10 µm thick Co-rich Co–Pt films (∼80:20 atomic ratio) hard magnetic films electroplated on silicon substrates are characterized at temperatures from 300 to 1000 K. With an increase in temperature up to 500 K, the coercivity and remanence of the films both decrease rapidly, dropping to only 10% of their respective as-deposited values. Above 500 K, the coercivity and remanence continue declining but at a slower rate, reaching nearly zero at 1000 K. Conversely, the saturation magnetization reduces by only 15% at 800 K and 40% at 1000 K from the as-deposited value. In addition to these measurements at elevated temperature measurements, thermal cycling tests are performed to examine the influence of various thermal exposures. Cycles up to 500 K are shown to have little impact on the film morphology but notably reduce the layer adhesion. Most importantly, a thermal cycle to just 400 K is shown to essentially destroy the hard magnetic properties. Because of these temperature sensitivities, Co-rich Co–Pt films may be significantly limited for end applications. (technical note)