Dynamics of the stress-mediated magnetoelectric memory cell N×(TbCo2/FeCo)/PMN-PT

Abstract

Stress-mediated magnetoelectric heterostructures represent a very promising approach for the realization of ultra-low energy Random Access Memories. The magnetoelectric writing of information has been extensively studied in the past, but it was demontrated only recently that the magnetoelectric effect can also provide means for reading the stored information. We hereby theoretically study the dynamic behaviour of a magnetoelectric random access memory cell (MELRAM) typically composed of a magnetostrictive multilayer N × (TbCo 2 /FeCo) that is elastically coupled with a <011> PMN-PT ferroelectric crystal and placed in a Wheatstone bridge-like configuration. The numerical resolution of the LLG and electrodynamics equation system demonstrates high speed write and read operations with an associated extra-low energy consumption. In this model, the reading energy for a 50nm cell size is estimated to be less than 5 aJ/bit.

Strain-mediated all-magnetoelectric memory cell

“…The calculated energy consumption for writing and reading operations was found equal to E =13 aJ/bit. This value is close to the previously calculated one, based on the model of the effective magnetoelectric medium [13] and is much lower than E = 6 fJ/bit, recently obtained experimentally in a MTJ-RAM of comparable size [16]. The stability of the equilibrium magnetic states "0" and "1" over time is ensured by the energetic barrier , where v is the volume of the cell [11].…”

“…For the description of the MELRAM dynamics we follow approach developed in [13]. The magnetization switch under electric tension is described by Landau-Lifshitz-Gilbert (LLG) equation:…”

“…(7) should be completed by the electrodynamic equations for the electrical circuit in which the magnetoelectric cell is embedded. Following [13], we consider the simplest circuit constituted by a Wheatstone bridge, as shown in Figure 4. In this case, the Vc voltage on the structure and the magnetoelectric signal VME across the diagonal of the bridge are described by the equations…”

“…In particular, the strain-mediated magneto-electric interaction is one of the most prospective principles of random-access memory that ensures ultra-low energy consumption of the devices [9][10][11]. This principle allows writing information in the magnetic subsystem as well as detecting the magnetic states by means of electric field pulses [12,13]. The design of the magnetoelectric memory (MELRAM) requires a detailed study of the strain-mediated interaction at the nano-scopic scale.…”

Ultrafast manipulation of magnetic anisotropy in a uniaxial intermetallic heterostructure TbCo2/FeCo

“…The FM/NM and FM/FM structures with in-plane anisotropy are used as spintronic THz emitters [19,20]. The FM/FM structures, such as TbCo 2 /FeCo multilayers with in-plane anisotropy are very prospective for creation of magnetoelectric random access memory (MELRAM) with ultra-low energy consumption about a few attojoule per bit [21]. The principle of operation of such devices is based on spin reorientation transitions (SRT) in the magnetic constituent, induced by short strain pulses generated by piezoelectric constituent elastically coupled with the structure.…”