Influence of temperature on the magnetic properties of electroplated L10 CoPt thick films

This paper reports the magnetic properties of 2 μm thick electroplated isotropic L10 CoPt films on silicon at temperatures ranging from 300 K to 790 K, as well as the room-temperature properties of the films after various thermal cycles. Electroplated equiatomic CoPt layers require a post-deposition annealing typically at ∼973 K to induce L10 ordering so that they exhibit hard magnetic properties at room temperature. However, the influence of temperature on these post-deposition annealed films is an important consideration for their utility in end applications. Here, a reversible temperature coefficient of remanence of −0.11% K−1 is measured along with a maximum operating temperature of 400 K (recovery to 95% of the initial remanence). The maximal energy density of the films is reduced by 50% at a temperature of 550 K. However, the original room-temperature magnetic properties are shown to be fully recoverable by remagnetization after various thermal cycles—800 K for 15 min in Ar, 373 K for 168 h in air, and 358 K for 168 h in air at 85% relative humidity. These investigations indicate that the electroplated L10 CoPt layers, like bulk, exhibit good thermal robustness, satisfying a key requirement for their use in end applications, such as magnetic microsystems.