Magnetic field sensing scheme using CoFeB/MgO/CoFeB tunneling junction with superparamagnetic CoFeB layer

Center for Frontier Materials, GIST, Gwangju 500-712, South Korea and Department of Materials Science and Engineering, GIST, Gwangju 500-712, South Korea
Applied Physics Letters (Impact Factor: 3.79). 11/2006; DOI: 10.1063/1.2370876
Source: IEEE Xplore

ABSTRACT The authors investigated the tunneling magnetoresistance (TMR) of Co Fe B / Mg O / Co Fe B tunnel junctions by varying the thickness (t Co Fe B ) of the top CoFeB layer. Linear and hysteresis-free switching was observed in junctions with t Co Fe B ≤10 Å , while normal tunneling behavior occurred for t Co Fe B ≫10 Å . The field sensitivity and the sensing field range were found to be controlled by varying the thickness of the sensing layer. This finding means that the magnetic tunneling junction (MTJ) provides a scheme for magnetic field sensing, which has a simple sensor design and low power consumption. The magnetic properties of the sensing layer with t Co Fe B ≤10 Å were found to show the characteristics of superparamagnetism. Although the detailed mechanism of TMR in MTJs with a superparamagnetic layer is not fully understood at present, this phenomenon is observed repeatedly. Therefore, this sensing scheme would be an alternative method for overcoming the problems in magnetic sensors with a crossed magnetization pattern.

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