Magnetic RAM (MRAM) memory is booming. It is non-volatile, energy-efficient, fast and non-degradable, whereas flash memory is limited to a few thousand writes. MRAM is already used as a cache memory or in some low-power or fast applications, such as microcontrollers. Its wider use would require further improvements in thermal stability, i.e. the retention of data over time, even at high temperatures.

The highly efficient Spin Transfer Torque (STT) MRAM could replace, e.g. computer’s DRAM. To do this, it would be necessary to be able to increase the density of the magnetic elements, which requires miniaturisation. However, the layers of ultra-thin and small-size MRAMs elements are very sensitive to thermal heating, which causes them to lose stored data.
Since 2018, researcher at IRIG [collaboration] have been developing a new type of STT-MRAM based on magnetic bits with a vertical shape, providing resistance against thermal effects. They have designed such a nanopillar with 20nm diameter, comprising the storage layer. The magnetization state of the nanopillar was monitored with the technique of electron holography. The outcome directly demonstrates this claim: magnetization is nearly insensitive to temperature, remaining largely homogeneous, vertical and symmetric. Consequently, the nanopillar remains unaffected by temperature thanks to the magnetostatic shape effect and its large volume.
The results confirm directly that vertical STT-MRAM is a viable route to lift limitations of the current MRAM technology, opening new markets for these memories such as in the automotive industry, or for high-density DRAM with low power consumption.


Left, vertical MRAM based on an iron-nickel nanopillar (pink). Right, magnetization inside the nanopillar, and the resulting stray field around it, both quite insentitive to temperature. Credit CEA​

Collaboration with the Electronics and Information Technology Laboratory of CEA-Grenoble (CEA-Leti), the Upstream Technological Platform (PTA), and the Platform for Nanocharacterisation (PFNC).