Crystal Structure and Magnetic Characteristics of Tb/Fe Multilayers
We have grown Tb/Fe multilayers with modulation wavelengths in the range of 10 to 200 A by alternately sputtering these components. The individual layer thicknesses were kept constant to within ±0.3% over the entire sample thickness of ≈0.2 μm by feedback control of the sputtering rates and microprocessor control of the substrate rotation. Composition of the samples was determined from calibrated sputtering rates, and was confirmed using Rutherford backscattering spectrometry. The layered structure was demonstrated by low angle x-ray diffraction. High angle x-ray results show that the Tb and Fe layers are polycrystalline for high modulation wavelengths, but are amorphous for low modulation wavelengths. A vibrating sample magnetometer was used to measure the coercivity and saturation magnetization over the temperature range 200 to 430 K. Comparing results for pure Fe, pure Tb, and Tb/Fe multilayers demonstrates that the Tb and Fe multilayers couple to form an antiferromagnetic film.