Crystal structure and its correlation to intrinsic and extrinsic magnetic properties of epitaxial hard magnetic Pr-Co films

Pulsed laser deposited epitaxial PrxCo100−x (x=8.7–27.6 at. %) thin films were systematically studied as a function of Pr content. Structural and magnetic measurements reveal different phases for specific composition ranges. In some cases, the phases observed are in contrast to their bulk counterparts. Uniaxial anisotropy at room temperature is observed in all the films enabling excellent hard magnetic properties. Polarization decreases monotonically with the increase of Pr content, whereas coercivity exhibits a broad maximum near the highly anisotropic PrCo5 composition. For the optimum combination of coercivity and polarization, the measured (BH)max reaches values of 310 kJ/m3, which exceeds the highest-energy product value reported for RE-Co (RE=rare-earth) systems. Temperature-dependent ac susceptibility measurements reveal that films with x=8.7–20.4 undergo a spin reorientation from easy axis to easy cone, but films with x=22.9–27.6 maintain their uniaxial anisotropy throughout the temperature range of investigation. From the comparison of the structural investigations and the spin reorientation temperature measurements, it is concluded that the spin reorientation temperature is insensitive to the change in the lattice parameter of the PrCo5±δ phase.