Magnetic properties and crystal structure of Ti/Ni superlattices (abstract) : The 5th Joint MMM−Intermag Conference

1089-7550

AIP Digital Archive

Physics

A series of periodic multilayer Ti/Ni thin films of the form (xTi/yNi)n were grown at room temperature by alternate deposition of elemental Ti and Ni onto glass substrates using dc-magnetron sputtering. The thicknesses of the individual Ti and Ni layers are given by x and y, respectively, and the total number of bilayer units is n. For this set of experiments, x was fixed at 2.8 nm while y was systematically varied from 2.4 to 154 nm. The product ny was held constant for all samples so that each film contained the same quantity of Ni. The growth rates of Ti and Ni were 0.14 and 0.32 nm/s, respectively. The multilayers were tested in the as-deposited state for magnetic properties using a vibrating sample magnetometer. These superlattices showed a variety of magnetic characteristics which were dependent on the thickness of the Ni layers. The coercivity of the multilayers declined with Ni layer thickness from a maximum of 80 Oe to a minimum of 7 Oe. A systematic reduction in saturation magnetization (Ms) with Ni layer thickness was also observed (for multilayers with y〈38 nm). In order to determine if the reduction in Ms could be attributed to a specific structural feature, a systematic study using transmission electron microscopy (imaging and electron diffraction) was made of the individual Ti/Ni and Ni/Ti bilayer units which comprise the superlattices. The bilayer units were grown under the same sputtering conditions used for the multilayers. Evidence was found for substantial strain (+4%) in the Ni layers and for the formation of Ni-Ti compounds presumably nucleated at the interfaces (the extra electron diffraction rings most closely match Ni3Ti).

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