Magnetization and its temperature dependence in compositionally modulated amorphous Fe70B30-Ag films

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Abstract
Compositionally modulated amorphous Fe70B30‐Ag films have been prepared by dc magnetron sputtering. The thickness of the magnetic layer (d) ranged from 3 to 90 Å, while the Ag layer thickness was always kept at four times as large. The multilayer structure is well established by the cross‐sectional transmission electron micrograph. The magnetic properties of the system were investigated with a SQUID magnetometer. The spontaneous magnetization (Ms) at T=8 K remains constant over the thickness range studied, indicating the absence of magnetically dead layers at the interfaces. The temperature dependence of Ms follows Bloch’s law for d≥6 Å, with the spin‐wave constant inversely proportional to d. This is explained by an interface effect on spin‐wave excitation. As the thickness is reduced to 4 Å, a linear temperature dependence of Ms is observed, indicating a magnetic 3D‐to‐2D transition.