Microstructure Evolution and First-Order Reversal Curve Analysis of the Interphase Coupling in SmCo Thick Film

Thick SmCo films of 500 nm thickness were deposited by radio frequency sputtering in W/SmCo/W structures on a Si substrate. After annealing at 650–750 °C, the as-grown soft amorphous structure transforms into a mixture of crystalline Sm ₂ Co ₁₇ and SmCo ₅ hard magnetic phases. Annealing at 650 °C leads to film crystallization with an average grain size of 64 nm, coercivity of 0.5 T, and remanence magnetization of about 0.5 T for a maximum applied field of 2 T. The remanence magnetization decreases by 20% upon annealing at 750 °C, whereas the average crystalline size and coercivity increase up to 73 nm and 1.1 T, respectively. Series of the first-order reversal curves recorded in the samples that were annealed at 650 °C and 750 °C demonstrate redistribution of the switching fields between the softer (Sm ₂ Co ₁₇₎ and harder (SmCo ₅ ) phases, depending on the strength of interphase interaction. Overall, the higher remanence and sizable coercivity of films annealed at 650 °C make them good candidates for the fabrication of micromagnets to be integrated in microelectromechanical systems.