Structure and magnetic properties of ferrimagnetic [Gd/Fe]n multilayer and GdxFe100−x thin films

The structural and magnetic properties of two series of [Gd(2, 4 nm)/Fe(t)]n multilayer films with varying Fe thickness were investigated and compared to those of amorphous ferrimagnetic GdFe alloys of the same corresponding composition. Transmission electron microscopy studies confirmed the high interface quality of both multilayer series. Furthermore, the microstructure was analyzed, revealing polycrystallinity in both Gd and Fe layers with strong (101̄0)-oriented textured growth of Gd particularly for the multilayer series with 2 nm Gd. Magnetic measurements confirm an out-of-plane magnetic easy axis in the alloy samples and an in-plane magnetic easy axis in all multilayer samples. Twisted spin states in samples with a low remanent magnetization were identified. Magnetic compensation points of both multilayer series are compared to those of the alloy samples. It was found that the dependence of the magnetic compensation point on effective Gd concentration in the series with 2 nm Gd closely resembles the strong dependence observed in the alloy counterparts. In contrast, a weaker dependence is revealed for the multilayer series with 4 nm Gd, which makes this system more robust against variations in composition required for applications.