Electrostatically Controlled Magnetization Rotation in Ferromagnet-Topological Insulator Planar Structures

An approach to the electrostatic control of $90^{\circ}$ magnetization rotation in the hybrid structures composed of topological insulators (TIs) and adjacent ferromagnetic insulators (FMI) is proposed and studied. The concept is based on TI electron energy variation with in-plane to put-of plane FMI magnetization turn. The calculations explicitly expose the effect of free energy variability in the form of the electrically controlled uniaxial magnetic anisotropy, which depends on proximate exchange interaction and TI surface electron density. Combining with inherent anisotropy, the magnetization rotation from in-plane to out-of-plane direction is shown to be realizable for 1.7~2.7 ns under the electrical variation of TI chemical potential in the range $\pm$ 100 meV around Dirac point. When bias is withdrawn a small signal current can target the out-of-plane magnetization instable state to the desirable direction of in-plane easy axis, thus the structure can lay the foundation for low energy nonvolatile memory prototype

Voltage Control of Electromagnetic Properties in Antiferromagnetic Materials

Dynamic modulation of electromagnetic responses is theoretically examined in dielectric antiferromagnets. While both magneto-electric and magneto-elastic coupling can achieve robust electrical control of magnetic anisotropy, the latter is considered in a bilayer structure with a piezoelectric material. Numerical calculations based on the frequency-dependent permeability tensor clearly illustrate that the anisotropy profile in the typical uniaxial or biaxial antiferromagnets such as NiO and Cr2O3 can be modified sufficiently to induce a shift in the resonance frequency by as much as tens of percent in the sub-mm wavelength range (thus, an electrically tunable bandwidth over 10's of GHz). The polarization of the electromagnetic response is also affected due to the anisotropic nature of the effect, offering a possibility to encode the signal. The intrinsic delay in switching may be minimized to the ns level by using a sufficiently thin antiferromagnets. Application to specific devices such as a band-pass filter further illustrates the validity of the concept

miR-132/212 knockout mice reveal roles for these miRNAs in regulating cortical synaptic transmission and plasticity

miR-132 and miR-212 are two closely related miRNAs encoded in the same intron of a small non-coding gene, which have been suggested to play roles in both immune and neuronal function. We describe here the generation and initial characterisation of a miR-132/212 double knockout mouse. These mice were viable and fertile with no overt adverse phenotype. Analysis of innate immune responses, including TLR-induced cytokine production and IFNβ induction in response to viral infection of primary fibroblasts did not reveal any phenotype in the knockouts. In contrast, the loss of miR-132 and miR-212, while not overtly affecting neuronal morphology, did affect synaptic function. In both hippocampal and neocortical slices miR-132/212 knockout reduced basal synaptic transmission, without affecting paired-pulse facilitation. Hippocampal long-term potentiation (LTP) induced by tetanic stimulation was not affected by miR-132/212 deletion, whilst theta burst LTP was enhanced. In contrast, neocortical theta burst-induced LTP was inhibited by loss of miR-132/212. Together these results indicate that miR-132 and/or miR-212 play a significant role in synaptic function, possibly by regulating the number of postsynaptic AMPA receptors under basal conditions and during activity-dependent synaptic plasticity

First-principles analysis of electron-phonon interactions in graphene

Article on first-principles analysis of electron-phonon interactions in graphene