Temperature and thickness dependent magnetostatic properties of [Fe/Py]/FeMn/Py multilayers
The magnetic properties of thin-film multilayers [Fe/Py]/FeMn/Py are investigated as a function of temperature and thickness of the antiferromagnetic FeMn spacer using SQUID magnetometry. The observed behavior differs substantially for the structures with 6-nm and 15-nm FeMn spacers. While the 15-nm-FeMn structure exhibits exchange pinning of both ferromagnetic layers in the entire measurement temperature interval from 5 to 300 K, the 6-nm-FeMn structure becomes exchange de-pinned in the vicinity of room temperature. The de-pinned state is characterized by a single hysteresis loop centered around zero field and having enhanced magnetic coercivity. The observed properties are explained in terms of finite-size effects and possibly ferromagnetic interlayer coupling through the thin antiferromagnetic spacer.