Magnetic memory cells associated with the stress-mediated magnetoelectric effect promise extremely low bit-writing energies. Most investigations have focused on the process of writing information in memory cells, and very few on readout schemes. The usual assumption is that the readout will be achieved using magnetoresistive structures such as Giant Magneto-Resistive stacks or Magnetic Tunnel Junctions. Since the writing energy is very low in the magnetoelectric systems, the readout energy using magnetoresistive approaches becomes non negligible. Incidentally, the magneto-electric interaction itself contains the potentiality of the readout of the information encoded in the magnetic subsystem. In this letter, the principle of magnetoelectric readout of the information by an electric field in a composite multiferroic heterostructure is considered theoretically and demonstrated experimentally using [N×(TbCo2/FeCo)]/[Pb(Mg1/3Nb2/3)O3](1−x)−[PbTiO3]x stress-mediated ME heterostructures.
The motion of a ferromagnetic domain wall in nanodevices is usually induced by means of external magnetic fields or polarized currents. Here, we demonstrate the possibility to reversibly control the position of a N eel domain wall in a ferromagnetic nanostripe through a uniform mechanical stress. The latter is generated by an electro-active substrate combined with the nanostripe in a multiferroic heterostructure. We develop a model describing the magnetization distribution in the ferromagnetic material, properly taking into account the magnetoelectric coupling. Through its numerical implementation, we obtain the relationship between the electric field applied to the piezoelectric substrate and the position of the magnetic domain wall in the nanostripe. As an example, we analyze a structure composed of a PMN-PT substrate and a TbCo 2 /FeCo composite nanostripe.
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.
A complex study of the electron transport and magnetic characteristics of epitaxial manganite films La0.7Ba0.3MnO3 (LBMO) was carried out under conditions of the crystal structure tension caused by a mismatch between the parameters of the LBMO crystal and the substrate. The epitaxial thin films with the thickness 40-100 nm were grown by pulsed laser deposition at T = 700-800 °C in pure oxygen pressure 0.3-1 mbar. The substrates (110) NGO, (001) STO, (001) LAO, and (001) LSAT were used. By comparison of the lattice parameter of LBMO targets with substrate's one, the lattice mismatches were derived. We used substrates in which the lattice parameter was less than for the LBMO crystal one. It is shown that the temperature dependence of the film resistance in the low-temperature region does not depend on the film stress and is in good agreement with the calculation that takes into account the interaction of carriers with magnetic excitations in the presence of strongly correlated electron states. A nonmonotonic temperature dependence of the resistance of an LBMO film deposited on ferroelectric crystals PMN-PT that was observed. This feature is typical for manganites, and indicating the presence of ferromagnetism in the system was observed.
Stratospheric sulfate aerosols play a key role on atmospheric chemistry
and Earth’s radiation budget, but their size distribution, a critical
parameter in climate models, is generally poorly-known. We address such
gap for the 2022 Hunga Tonga-Hunga Ha apai (HT-HH) volcanic eruption by
exhaustively analyzing photometric observations from the worldwide
open-access AERONET network. We document a rapid growth of HT-HH sulfate
aerosols in the days following eruption, faster than observed for other
stratospheric eruptions, likely due to the exceptional hydration of the
stratosphere by this phreatomagmatic eruption. An unusual aerosol fine
mode (peak radius in 0.3-0.5 µm) is identified at >20
stations of the southern hemisphere until December 2022 (time of
writing). Nevertheless, one year after eruption, HT-HH sulfate aerosols
remain smaller than 1991 Pinatubo particles. Smaller aerosols
backscatter more efficiently visible light and sediment more slowly than
larger particles, implying stronger and longer-lasting negative
radiative forcing.
Stratospheric sulfate aerosols play a key role on atmospheric chemistry
and Earth’s radiation budget, but their size distribution, a critical
parameter in climate models, is generally poorly-known. We address such
gap for the 2022 Hunga Tonga-Hunga Ha’apai (HT-HH) volcanic eruption by
exhaustively analyzing a set of satellite observations together with
photometric ground observations from the worldwide open-access AERONET
network. We document a rapid growth of HT-HH sulfate aerosols in the
days following eruption, faster than observed for other stratospheric
eruptions, likely due to the exceptional hydration of the stratosphere
by this phreatomagmatic eruption. An unusual aerosol fine mode (peak
radius in 0.3-0.5 microns) is identified at 20 stations of the southern
hemisphere until May 2023 (time of writing). Nevertheless, 1.4 years
after eruption, HT-HH sulfate aerosols remain smaller than 1991 Pinatubo
particles. Smaller aerosols backscatter more efficiently visible light
and sediment more slowly than larger particles, implying stronger and
longer-lasting negative radiative forcing.
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