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The Giant VCMA Effect for Novel MRAM Applications
Book - Dissertation
This project aims to make possible the next generation of magnetic memory (MRAM) replacing the present Spin-Transfer Torque (STT) current controlled STT MRAM by a low power, nonvolatile voltage controlled MRAM. With voltage controlled MRAM, we aspire to reduce future chip power consumption, important for the future of nanoelectronics. Apart from reducing computing's energy footprint, increasing energy efficiency is also crucial to realise the vision of ambient intelligence and the internet of things.
We will investigate the recently discovered Voltage-Controlled Magnetic Anisotropy (VCMA) effect [1] [2] for writing MRAM bits. In VCMA, the application of an electric field at a ferromagnet-insulator interface results in a change in magnetic anisotropy, which can result in a change of magnetisation orientation and stored bit value. The boosting of the VCMA effect will be investigated in this PhD project. The VCMA effect writes a bit by removing the energy barrier which guarantees the retention of the memory state. The present VCMA effect observed in CoFeB/MgO stacks is too weak to remove barriers guaranteeing sufficient retention for non-volatile memory. A much larger VCMA effect will open doors to a nonvolatile, low power voltage controlled MRAM.
This project will focus on uniquely combining state-of-the-art materials into VCMA material stacks and tailor the crucial insulator-ferromagnet interface. Specialized thin film materials of the highest quality will be combined at imec to search for a boosted VCMA effect. Specialized electrical and magnetic characterization will be carried out to probe the origins and potential of this recently discovered phenomenon. [1] T. Maruyama, Y. Shiota, T. Nozaki, K. Ohta, N. Toda, M. Mizuguchi, A. A. Tulapurkar, T. Shinjo, M. Shiraishi, S. Mizukami, Y. Ando and Y. Suzuki, Nature nanotechnology, vol. 4, p. 158, 2009. [2] M. Weisheit, S. Fähler, A. Marty and Y. Souche, Science, vol. 315, p. 349, 2007. [3] D. Chiba, M. Sawicki, Y. Nishitani, Y. Nakatani, F. Matsukura and H. Ohno, 'Magnetization vector manipulation by electric fields,' Nature, vol. 455, p. 515, 2008.
This project will focus on uniquely combining state-of-the-art materials into VCMA material stacks and tailor the crucial insulator-ferromagnet interface. Specialized thin film materials of the highest quality will be combined at imec to search for a boosted VCMA effect. Specialized electrical and magnetic characterization will be carried out to probe the origins and potential of this recently discovered phenomenon. [1] T. Maruyama, Y. Shiota, T. Nozaki, K. Ohta, N. Toda, M. Mizuguchi, A. A. Tulapurkar, T. Shinjo, M. Shiraishi, S. Mizukami, Y. Ando and Y. Suzuki, Nature nanotechnology, vol. 4, p. 158, 2009. [2] M. Weisheit, S. Fähler, A. Marty and Y. Souche, Science, vol. 315, p. 349, 2007. [3] D. Chiba, M. Sawicki, Y. Nishitani, Y. Nakatani, F. Matsukura and H. Ohno, 'Magnetization vector manipulation by electric fields,' Nature, vol. 455, p. 515, 2008.
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