Magnetic tunnel junctions (MTJs) attract considerable attention in the field of spintronics since they show large tunnel magneto-resistance (TMR), which is important for application in devices such as hard disks, magnetic RAM, and magnetic sensors. Here, a novel way of characterizing tunnel junctions and materials used in MTJs is investigated: current-in-plane-tunneling (CIPT). This technique allows the use of unpatterned junctions. Moreover, since these measurements are local in nature, the effect of varying a junction parameter (for example barrier thickness) can be investigated in one single sample. In this thesis, a dedicated CIPT setup, able to measure (magnetic field dependent) sheet resistances with micron-sized probes, is designed and built. Then a number of different experiments are performed to demonstrate the successful characterization of various materials like NiO, MgO, and AlOx. We also report a direct observation of TMR using such materials. For applications in industry, micro-structured MTJs are used. When the sample area gets smaller, a deviation in the measured sheet resistance is observed. Using theoretical considerations, we show that these CIPT measurements can be corrected for these deviations. We believe that this CIPT setup presents new opportunities to explore new avenues in the field of spintronics.
|Date of Award||30 Apr 2008|
|Supervisor||P.V. Paluskar (Supervisor 1) & Henk J.M. Swagten (Supervisor 2)|