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2019-3-28

A team of researchers from The University of Tokyo, Murata Manufacturing Co., Ltd., and Osaka University succeeded in fabricating CoFeB/MgO-based magnetic tunnel junction (MTC) directly on an organic flexible substrate.

A magnetic tunnel junction (MTJ), a component consisting of two ferromagnets separated by a thin insulator, is a spintronics device widely used for highly sensitive magneto-resistive heads for hard disk drives and non-volatile memory-based mass storage devices. In particular, junction devices in which CoFeB is used for magnetic layers and MgO is used for the insulating layer (tunnel barrier) are widely used in commercially available devices; however, these junction devices are formed on rigid semiconductors and usage under conditions of external stress was not assumed.

In this study, the team succeeded in fabricating a CoFeB/MgO-based MTJ, a general-purpose spintronics device, directly on a flexible organic sheet, a world first. Although it was confirmed that the tensile strain was actually applied to the MTJ by stretching the substrate on which the MTJ was placed, the tunnel magnetoresistance (TMR) ratio didn’t change at all and the device was not destroyed, which showed that the device had good strain endurance. The device was also able to withstand high temperature processes of 350 °C.

Because this flexible MgO barrier MTJ can be fabricated using the similar method of making conventional MTJs on rigid Si substrates, it undoubtedly has a great potential for a wide range of applications. Compared to conventional devices fabricated on rigid substrates, this flexible spintronics can endow mechanical functions to spintronics devices, which allows for the improvement of strain gauge sensitivity and placement of energy-saving magnetic memories on flexible devices, developing applications to adapt to IoT society.

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The Article, “CoFeB/MgO-based magnetic tunnel junction directly formed on a flexible substrate” was published in Applied Physics Express at DOI: https://doi.org/10.7567/1882-0786/ab0dca.


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