A multilevel nonvolatile magnetoelectric memory

Abstract

The coexistence and coupling between magnetization and electric polarization in multiferroic materials provide extra degrees of freedom for creating next-generation memory devices. A variety of concepts of multiferroic or magnetoelectric memories have been proposed and explored in the past decade. Here we propose a new principle to realize a multilevel nonvolatile memory based on the multiple states of the magnetoelectric coefficient (α) of multiferroics. Because the states of α depends on the relative orientation between magnetization and polarization, one can reach different levels of α by controlling the ratio of up and down ferroelectric domains with external electric fields. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure confirm that the states of α can be well controlled between positive and negative by applying selective electric fields. Consequently, two-level, four-level, and eight-level nonvolatile memory devices are demonstrated at room temperature. This kind of multilevel magnetoelectric memory retains all the advantages of ferroelectric random access memory but overcomes the drawback of destructive reading of polarization. In contrast, the reading of α is nondestructive and highly efficient in a parallel way, with an independent reading coil shared by all the memory cells.

Assessing the Nature of Collisions of Coronal Mass Ejections in the Inner Heliosphere

“…But, for the data points corresponding to inelastic (0<e<1) nature of collision, only 39.5% have the values of u 12exs larger than the values of u 12cjr . Thus our finding is in agreement with that previously conceptualized in Shen et al (2012Shen et al ( , 2016.…”

“…As suggested in earlier studies by Shen et al (2012Shen et al ( , 2016, we examined the characteristic of collision with relative approaching speed of the centroids of the CMEs along the line joining their centroids (u 12cjr ) and the sum of their expansion speed (u 12exs ) at the beginning of collision. The top and bottom of the third panel (from the left) of Figure 4 shows the variation in e and σ values.…”

“…CME-CME interaction has been studied for more than a decade since its first observational evidence provided by Gopalswamy et al (2001) using the Large Angle and Spectrometric Coronagraph (LASCO; Brueckner et al 1995) on board the SOlar and Heliospheric Observatory (SOHO). The magnetohydrodynamics (MHD) numerical simulations have attempted to address the physical mechanism in CME-CME interaction, CME-CME driven shock interactions and their consequences (Vandas et al 1997;Vandas & Odstrcil 2004;Gonzalez-Esparza et al 2004;Lugaz et al 2005;Wang et al 2005;Xiong et al 2006Xiong et al , 2007Xiong et al , 2009Lugaz et al 2013;Shen et al 2013Shen et al , 2014Niembro et al 2015;Shen et al 2016). Realizing the importance of studying the CME-CME interaction and on availability of wide angle imaging observations of Heliospheric Imagers (HIs) with Coronagraphs (CORs) on board SECCHI/STEREO, almost a dozen cases of interacting CMEs have been reported in the literature in the last 5 years (e.g., Harrison et al 2012;Liu et al 2012;Lugaz et al 2012;Möstl et al 2012;Martínez Oliveros et al 2012;Shen et al 2012;Temmer et al 2012;Webb et al 2013;Ding et al 2014;Lugaz & Farrugia 2014;Mishra et al 2015a;Colaninno & Vourlidas 2015).…”

“…Earlier studies on different candidate of interacting CMEs, using the mass and kinematics estimates from multiple viewpoint observations of STEREO, have posed a question as to what decides the nature of collision to vary from super-elastic (Shen et al 2012(Shen et al , 2013Colaninno & Vourlidas 2015;Shen et al 2016) to inelastic (Temmer et al 2012;Lugaz et al 2012;Mishra et al 2015a,b). There were several limitations in some of these studies, such as no consideration of oblique collision scenarios in threedimension (3D), expansion speeds, and angular widths of the CMEs.…”

The first in situ observation of torsional Alfvén waves during the interaction of large-scale magnetic clouds

“…The various results obtained from studies have justified CME-CME collision as an in-elastic/elastic collision or super-elastic collision e.g. (Lugaz et al 2012;Shen et al 2012;Mishra et al 2017;Shen et al 2016;Lugaz et al 2017). The magnetohydrodynamics (MHD) numerical simulations have striven to understand the physical mechanism involved in CME-CME interaction, CME-CME driven shock interactions and their consequences e.g.…”