Magnetic Properties of ${{\hbox {Sm}}\hbox {-}{\hbox {Co}}/\alpha \hbox {-}{\hbox {Fe}}}$ Nanocomposite Thick Film-Magnets at Room and High Temperatures

Sm_xCo₅/α-Fe multilayered structures were synthesized by the pulsed laser deposition (PLD) method from rotating composite targets composed of Sm_xCo₅ (x = 1-5) and α-Fe segments. The deposited films were approximately 10 μm in thickness. Transmission electron microscopy observations revealed that as-deposited films were composed of Sm-Co and α-Fe layers, 780 layers in total, with the well-controlled thickness of approximately 10 nm, and they are crystallized into structures composed of Sm-Co and α-Fe nanograins. The (BH)_max versus Sm/(Sm+Co) curve at room temperature showed clear peaks and the (BH)_max value of 100 kJ/m³ was obtained. Although the obtained (BH)max value of Sm-Co/α-Fe nanocomposite thick film-magnets was comparable to that of Nd-Fe-B/α-Fe at room temperature, it exceeded those of Nd-Fe-B/α-Fe nanolayered magnets and rapidly quenched (Nd, Dy)-Fe-B flakes at 150°C. The large (BH)_max value of the Sm-Co/α-Fe nanocomposite thick film-magnet at 150°C can be attributed to its small temperature coefficient of coercivity, -0.34%/°C.