Magnetism of $L1_{0}{\rm Fe}_{50-{\rm x}}{\rm Co}_{\rm x}{\rm Pt}_{50}$ Films

Films of L1₀-structure Fe_50-xCo_xPt₅₀ films are synthesized by co-sputtering Fe, Co and Pt on (001) MgO substrates and Si substrates with in-situ heating at 830°C. The nanostructures and magnetic properties of the films are characterized by X-ray diffraction, transmission electron microscopy and SQUID. The compositions of the samples Fe_50-xCo_xPt₅₀ are designed to maintain an atomic (Fe+Co):Pt ratio of 50:50 while increasing the Co content in each successive sample. In all samples, the X-ray diffraction patterns from samples on MgO substrate exhibit three strong peaks, namely L1₀Fe_50-xCo_xPt₅₀ (001), (002) and MgO (002). The X-ray and electron diffraction patterns from untextured samples deposited on Si substrates can be indexed using the L1₀-structure, being consistent with the result of samples on MgO substrate. Hysteresis-loop measurements show that with increase of the Co concentration from 0 to 15 at%, the saturation magnetization M_s increases from 1017 emu/cm³ to 1165 emu/cm³, the coercivity decreases from 30 kOe to 14 kOe, and anisotropy decreases from 67 Merg/cm³ to 46 Merg/cm³. The nominal maximum energy products are in the range of 39-41 MGOe.