Evolution of Magnetic Anisotropy With Sm Contents in Sm–Co Thin Films

Abstract

In this paper, the evolution of magnetic anisotropy as a function of Sm contents in buffer-free Sm-Co thin films grown by molecular beam epitaxy is investigated. From the soft magnetic Sm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> phase, the anisotropy evolves to the hard magnetic SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> phase with a distinct perpendicular anisotropy and a maximum magnetic anisotropy energy of 1.67 MJ/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> as measured by torque magnetometry at 300 K. For SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> , a saturation magnetization of 845 emu/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , close to the bulk single crystal value is achieved, while a squareness ratio close to unity is measured in the hysteresis curve perpendicular to the film plane. Previously grown YCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> and CeCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> thin films with perpendicular anisotropy show a considerably reduced uniaxial anisotropy as well as a reduced squareness ratio as compared to SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> . These results demonstrate that the magnetic parameters of rare earth-cobalt thin films can be adapted according to the requirements of applications such as magnetic recording.