November 29-December 4, 2015 | Boston
Meeting Chairs: T. John Balk, Ram Devanathan, George G. Malliaras, Larry A. Nagahara, Luisa Torsi
The combination of high speed and non-volatility of perpendicular Spin-Transfer-Torque Magnetic Random Access Memories (pSTT-MRAMs) promises a significant reduction of computing power, making this technology particularly attractive for mobile and Internet-of-Things applications .In this talk, we will present recent advances in the development of perpendicular Magnetic Tunnel Junctions (pMTJs) at TDK-Headway Technologies , which have enabled the demonstration of fully functional 8Mb pSTT-MRAM chips with sub-5ns writing . Furthermore, we will discuss the physics of current-induced switching and thermal stability in pMTJs devices, in comparison with writing and data retention properties of 8Mb test chips .
Heteroepitaxial strain engineering is an essential tool in strongly correlated systems for investigating fundamental coupling effects and for more practical control of thin film properties. We demonstrate that the length of a single axis in an epitaxial CoFe2O4 (CFO) film can be controlled by strain doping helium into the lattice which in turn allows fine control over the magnetic easy axis through induced magnetostriction. Compressively strained thin films of CFO are grown coherently on MgO substrates and show pronounced out-of-plane magnetic anisotropy. Successive doping of the CFO films with He using a commercial ion gun results in an expansion of the out-of-plane lattice parameter while maintaining in-plane epitaxial lock to the substrate. We observe a continuous rotation of the magnetic easy axis towards the film plane with increasing unit cell tetragonality. A vacuum anneal above 500 °C is sufficient to evacuate the He from the lattice and return it to the pristine state. The results are in agreement with the strain-induced change of the magnetic anisotropy due to the large negative magnetostriction of CFO and demonstrates that strain doping via He implantation is an elegant path to tune desired characteristics of transition metal oxide thin films.This work was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division.
As existing memory systems approach fundamental limitations, ultra-thin uniform and conformal PZT films are needed for next-generation ultralow-power voltage-controlled non-volatile magnetoelectric RAM devices. By utilizing the magnetoelectric effect, where an electric field or voltage can be used to control the magnetization switching (instead of current), the writing energy can be reduced, resulting in increased memory density. Previous research has shown that the voltage-controlled magnetic anisotropy (VCMA) effect increases with the capacitance of the stack. Therefore, integr