Suppression of Sm Segregation and Improvement in Thermal Stability by Introducing Ru Underlayer in Co–Sm Amorphous Films

Abstract

Ru underlayer effects on the thermal stability of the magnetic properties in Co-Sm amorphous films have been investigated in terms of its robustness for the thermal-process in the fabrication of GHz band micro-magnetic devices. The anisotropy magnetic field H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> of the Co-Sm film was tending to decrease with an increase in the annealing temperature, but the reduction in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> due to thermal-process became small by introducing the Ru underlayer. The high-resolution transmission electron microscopy (HR-TEM) observations revealed the presence of nanosized crystalline Sm segregation at the interface between the Co-Sm film and SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si substrate in the films without Ru underlayer, while there is no Sm segregation in the film with Ru underlayer. Sm segregation and the subsequent thermally induced phase-separation are one of the factors for the reduction in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> . Ru underlayer effectively prevents the segregation of crystalline Sm and the resulting reduction in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> . High-frequency magnetic property of Co-Sm film with Ru underlayer was superior to that without Ru underlayer for same annealing condition.