This study reports an alternative method for measuring the magnetoresistance of unpatterned magnetic tunnel junctions similar to the current-in-plane tunneling (CIPT) method. Instead of using microprobes, a series of point contacts with different spacings are coated on the top surface of the junctions and R-H loops at various spacings are then measured by the usual four-point probe method. The values of magnetoresistance and resistance-area products can be obtained by fitting the measured data to the CIPT theoretical model. The test results of two types of junctions were highly similar to those obtained from standard CIPT tools. The proposed method may help to accelerate the process for evaluating the quality of magnetic tunnel junctions when commercial CIPT tools are not accessible.
Interlayer dipolar coupling is an important aspect in magnetic switching devices from the application point of view. Here, we identify various sources affecting the interlayer dipolar coupling in CoFeB-based perpendicular magnetic tunnel junctions (pMTJs). By changing the MgO tunnel barrier layer thickness, we show that it plays a crucial role in controlling the dipolar coupling between the CoFeB reference and free layers and affects the magnetic properties of pMTJ. Moreover, changes in thickness of the bottom electrode layer affect the interlayer coupling strength and change the magnetic anisotropy of the free layer from perpendicular to in-plane direction. Furthermore, it is observed that the smaller the cell size of such MTJs, the more dominating the coupling strength which is formed by stray fields. These are some of the crucial parameters which need to be investigated during the device fabrication process for optimum device performance.
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