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

Samsung Advanced Institute of Technology, Usan-ri, Gyeonggi-do, South Korea
Applied Physics Letters (Impact Factor: 3.3). 11/2006; 89(16):163119 - 163119-3. DOI: 10.1063/1.2370876
Source: IEEE Xplore


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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    • "Clear evidence is found for perpendicular magnetic anisotropy in the Pd/CoFeB/Pd bilayer system up to a CoFeB thickness of 0.6 nm. However, in the sputtered MgO/CoFeB/Pd system, where the CoFeB layer is amorphous, it may be superparamagnetic at room temperature despite the fact that it is a continuous film [15]. High-temperature annealing does not enhance the perpendicular anisotropy, which is not the case in the MgO/CoFeB/Pt system. "
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    IEEE Transactions on Magnetics 07/2010; 46(6-46):2116 - 2118. DOI:10.1109/TMAG.2010.2044374 · 1.39 Impact Factor
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    Applied Physics Letters 09/2007; 91(10). DOI:10.1063/1.2779241 · 3.30 Impact Factor
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    Journal of Applied Physics 05/2008; 103(7-103):07B526 - 07B526-3. DOI:10.1063/1.2838851 · 2.18 Impact Factor
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