AIST Stories No1
From AIST to the Innovative World8A giant TMR effect in an MTJ using a crystal of magnesium oxide (an MgO–MTJ) was theoretically predicted (in the USA and the UK). Major research institutions in Europe and America try to realize the effect, with no success at all.20012003The giant TMR effect is realized at AIST.2005Technologies for mass production of MgO–MTJs are developed.The New Energy and Industrial Technology Develop-ment Organization (NEDO) starts its Nanotechnology Challenge Project.2004Development in collaboration with CANON ANELVA begins.2014Toshiba is expected to start shipping engineering samples of large-capacity MRAMs.2006NEDO starts its Spintronics Non-volatile Devices Project-20092010Circuit board technology for large-capacity MRAMs is developed by Toshiba and AIST.2007MgO-TMR heads are commercialized (Fujitsu, AIST, CANON ANELVA)Development historydevelopment with CANON ANELVA Corporation (known as ANELVA at the time), a manufacturer of equipment for producing components for HDD magnetic recording heads. He asked them to develop a base structure that would make “the unknown” possible.“However, they came back with a counter-proposal to develop a method for growing my crystal on a conventional base structure. So I decided to work on that.”The process of development was blessed with several strokes of luck, and before long he had discovered a revolutionary solution. He found that adding boron (B) to a cobalt–iron (CoFe) alloy, the standard material for ferromagnetic electrodes, made it possible to form an amorphous thin film of a CoFeB alloy, and the crystalline layer of magnesium oxide could be grown on that film. In the example of the marbles, this is like being able to form a layer of soft clay on the marbles arranged in the triangular pattern and then stack marbles in the square pattern on that layer.“Then, not only did we solve the problem of growing the MTJ films on a foundation with a different symmetry, but we succeeded in mass-producing them using CANON ANELVA’s production equipment. My basic research was suddenly transformed into a mass production technology.”That was the moment that the technology the world had been waiting for was launched. Through CANON ANELVA, transfer of the technology to the industrial world progressed smoothly, and HDD magnetic heads capable of reading at recording densities several times greater than previously were commercialized as soon as 2007. As mentioned above, their global market share is now 100%.“Between basic research and commercialization, there is a ▲An MTJ film using magnesium oxide. The films were produced on special small substrates at a rate of about one a day.Tunnel magnetoresistance effect gets bigger and biggerGiant TMRYear600Crystalline (001) MgO tunnel barrier 5004003002001001995200020050MR ratio at room temperature (%)Amorphous Al-Otunnel barrierIBM AIST  AIST  OrientedpolycrystallineMTJSingle crystalline MTJMgO(001)FeCo(001)MgO(001)Fe(001)Yuasa, Jpn. J. Appl. Phys. 43, L558(2004). Yuasa, Nature Mater. 3, 868 (2004).Parkin, Nature Mater. 3, 862(2004).