Lun 12 Giu
Altri Eventi

Electrolyte gating of magnetic materials: a new paradigm for low-power memory applications and neuromorphic systems

On Monday, 12 June 2023 the meeting entitled "Electrolyte gating of magnetic materials: a new paradigm for low-power memory applications and neuromorphic systems" part of the INRiM seminar series, will be held online.


Manipulating magnetism
with voltage has an enormous potential to boost energy efficiency in nanoscale device applications since Joule heating effects associated with flowing electric current (needed to generate magnetic fields) are minimized. Among various types of magnetoelectric materials, porous alloys and oxides have gained considerable attention due to their very large surface-area-to-volume ratio which allows for large electric surface charge accumulation and eventual electrochemical reactions. They have recently demonstrated the possibility to induce considerable reversible, non-volatile changes in the magnetic properties (coercivity, magnetic moment) of nanoporous films consisting of metal alloys (e.g., CuNi, FeCu) or oxides (e.g., FeOx, CoFe2O4), by applying an electric field through a liquid electrolyte gate at room temperature [1,2].

In turn, they have made progress in the field of magneto-ionics, i.e., voltage-driven ion transport in magnetic materials, which has traditionally relied on controlled migration of oxygen or lithium ions. Here, will show that voltage-driven transport of nitrogen ions can be triggered at room temperature in transition metal nitride (CoN, FeN) films via liquid electrolyte gating [3,4].

Nitrogen magneto-ionics can induce reversible ON-OFF transitions of ferromagnetic states at faster rates and lower threshold voltages than oxygen magneto-ionics. This is due to the lower activation energy for ion diffusion and the lower electronegativity of nitrogen compared to oxygen. Remarkably, and in contrast to oxygen magneto-ionics, nitrogen transport occurs uniformly through a plane-wave-like migration front, without the assistance of diffusion channels, particularly interesting for the implementation of multi-stack memory devices.
Furthermore, will show that nitrogen magneto-ionics can be used to emulate some important neuromorphic functionalities. By cumulative effects of DC and pulsed voltage actuation (at frequencies in the range 1 – 100 Hz), learning, memory retention, forgetting and self-learning by maturity (post-stimulated learning) can be mimicked.
This latter effect can serve as a logical function for the device to decide between self-learning or forgetting emulation, at will, without any additional electric voltage input. This constitutes a novel approach to emulate some specific neural functionalities (e.g., learning under deep sleep), that are challenging to achieve using other classes materials currently employed for neuromorphic computing applications.

Speaker: professor Jordi Sort - Universitat Autònoma de Barcelona and Institució Catalana de Recerca i Estudis Avançats (ICREA).