Structure and Electrical Resistivity of Sputtered Tb/Ti and Tb/Si Magnetic Multilayers

A study of structural properties and electrical resistivity of [Tb/Ti]_n and [Tb/Si]_n multilayers deposited by rf-sputtering is presented. The transmission electron microscopy data show that the Tb layers with Ti spacers remain nanocrystalline down to a multilayer thickness of 1.5 nm. In this case titanium does not form a mixture with terbium and there is a tendency of granular structure formation at very low terbium layer thicknesses. In contrast, for the Tb/Si multilayered nanostructures interdiffusion of terbium and silicon layers takes place leading to the formation of amorphous Tb-Si alloys. Resistance was measured in the temperature range 2 to 300 K, showing metallic behavior when the Tb layer thickness, L _Tb, was >1.5 nm for [Tb/Ti]_n multilayers and for L _Tb = 12 nm in the [Tb/Si]_n samples. In the other cases, a negative temperature coefficient of the resistance was observed. The behavior of electrical resistivity has been correlated with structural properties of the multilayers. Temperature dependences of the electrical resistance for Tb/Ti and Tb/Si multilayers were studied both without magnetic field and in the presence of magnetic field of 90 kOe.