Typical Kondo insulators (KIs) can have a nontrivial ${\mathbb{Z}}_2$ topology because the energy gap opens at the Fermi energy ($E_F$) by a hybridization between odd- and even-parity bands. ${\mathrm{SmB}}_6$ deviates from such KI behavior, and it has been unclear how the insulating phase occurs. Here, we demonstrate that charge fluctuations are the origin of the topological insulating phase in ${\mathrm{SmB}}_6$. Our angle-resolved photoemission spectroscopy results reveal that with decreasing temperature the bottom of the $d\text{−}f$ hybridized band at the $\overline{X}$ point, which is predicted to have odd parity and is required for a topological phase, gradually shifts from below to above $E_F$. We conclude that ${\mathrm{SmB}}_6$ is a charge-fluctuating topological insulator.

The paper considers SnO₂and In₂O₃thin films as materials for the design of solid-state conductometric ozone sensors in depth. In particular, the present review covers the analysis of the fundamentals of SnO₂- and In₂O₃-based conductometric ozone sensor operation. The main focus is on the description of mechanisms of ozone interaction with metal oxides, the influence of air humidity on sensor response, and processes that control the kinetics of sensor response to ozone.

The authors investigated the tunneling magnetoresistance (TMR) of $\mathrm{Co}\mathrm{Fe}\mathrm{B}∕\mathrm{Mg}\mathrm{O}∕\mathrm{Co}\mathrm{Fe}\mathrm{B}$ tunnel junctions by varying the thickness $\left(t_{\mathrm{Co}\mathrm{Fe}\mathrm{B}}\right)$ of the top CoFeB layer. Linear and hysteresis-free switching was observed in junctions with $t_{\mathrm{Co}\mathrm{Fe}\mathrm{B}}⩽10\mathrm{\AA }$ , while normal tunneling behavior occurred for $t_{\mathrm{Co}\mathrm{Fe}\mathrm{B}}>10\mathrm{\AA }$ . The field sensitivity and the sensing field range were found to be controlled by varying the thickness of the sensing layer. This finding means that the magnetic tunneling junction (MTJ) provides a scheme for magnetic field sensing, which has a simple sensor design and low power consumption. The magnetic properties of the sensing layer with $t_{\mathrm{Co}\mathrm{Fe}\mathrm{B}}⩽10\mathrm{\AA }$ were found to show the characteristics of superparamagnetism. Although the detailed mechanism of TMR in MTJs with a superparamagnetic layer is not fully understood at present, this phenomenon is observed repeatedly. Therefore, this sensing scheme would be an alternative method for overcoming the problems in magnetic sensors with a crossed magnetization pattern.

This article describes in detail the SnO₂ and In₂O₃ metal oxides as materials for designing solid state conductometric ozone sensors. The main focus of this article is on the description of the SnO₂ and In₂O₃ films' structural parameters important for gas sensor design and on the establishment of the main regularities of the film parameters influence on the sensor characteristics. Advantages and disadvantages of approaches used for optimization of ozone sensor parameters are also analyzed_. In particular, surface modification, bulk doping of SnO₂ and In₂O₃, and the use of 1D structures and hybrid materials are considered. The main factors, controlling parameters of SnO₂- and In₂O₃-based ozone sensors, are determined, and recommendations for the process of the SnO₂ and In₂O₃ films deposition, facilitating the search of the film parameters and the fabrication technologies that optimize the ozone sensor performance, are formulated.

Spin-orbit torque has attracted considerable attention as a means to overcome limits of devices based on spin-transfer torque. However, a small magnetic field that is collinear to the current flow must be applied to break symmetry and induce deterministic current-induced magnetization switching. Recently, a junction utilizing interlayer coupling mediated by a Ru spacer layer between two CoFe layers was designed for symmetry breaking and exhibited current-induced magnetization switching without a magnetic field. Here, we demonstrate zero-field current-induced switching of the perpendicular magnetization of a Co layer that is indirectly coupled with a CoFe layer via a Ta spacer. The weak interlayer coupling exhibited by Ta allows the layer thickness to be relatively small (≈0.5 nm), enabling appropriate interlayer coupling to induce spin-orbit torque for current-induced magnetic switching. External magnetic field effects on switching characteristics show that the current switching process is quite stable against external environments.