  We report the compositional and temperature dependence of magnetic
compensation in amorphous GdFeCo films. Magnetic compensation is attributed to
the competition between antiferromagnetic coupling of rare-earth with
transition-metal (TM) ions and ferromagnetic interaction between the TM ions.
The low-Gd region from 20 to 34 at. % was found to exhibit compensation
phenomena characterized by a low saturation magnetization and perpendicular
magnetic anisotropy (PMA) near the compensation temperature. Compensation
temperature was not observed in previously unreported high-Gd region from 52 to
59 at. %, in qualitative agreement with results from recent model calculations.
However, low magnetization was achieved at room temperature, accompanied by a
large PMA with coercivity reaching ~6.6 kOe. The observed perpendicular
magnetic anisotropy of amorphous GdFeCo films probably has a structural origin
consistent with certain aspects of the atomic-scale anisotropy. Our findings
have broadened the composition range of transition metal-rare earth alloys for
designing PMA films, making it attractive for tunable magnetic anisotropy in
nanoscale devices.
