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Since the resurgence of multiferroics research, significant advancement has been made in the theoretical and experimental investigation of the electric field control of magnetization, magnetic anisotropy, magnetic phase, magnetic domains, and Curie temperature in multiferroic heterostructures. As a result of these advances, multiferroic heterostructures are on a trajectory to impact spintronics applications through the significantly reduced energy consumption per unit area for magnetization switching (1–500 μJ cm−2) when compared to that of current-driven magnetization switching (0.2–10 mJ cm−2). Considering this potential impact, it becomes necessary to understand magnetoelectric switching dynamics and characteristic switching times. The body of experimental work investigating magnetoelectric switching dynamics is rather limited, with the majority of room temperature converse magnetoelectric switching measurements reported having employed relatively long voltage pulses. Recently, however, the field has started to consider the kinetics of the switching path in multiferroic (and ferroelectric) switching. Excitingly, the results are challenging our understanding of switching processes while offering new opportunities to engineer the magnetoelectric effect. Considering the prospects of multiferroics for beyond-CMOS applications and the possible influence on operational speed, much remains to be understood regarding magnetoelectric switching kinetics and dynamics, particularly at reduced dimensions and under the influence of boundary effects resulting from strain, electrostatics, and orientation. In this article, we review magnetoelectric switching in multiferroic heterostructures for the electric field control of magnetism. We then offer perspectives moving toward the goal of low energy-delay spintronics for computational applications. [ABSTRACT FROM AUTHOR]

Compelling evidence suggests distinct correlated electron behavior may exist only in clean 2D materials such as 1T-TaS2. Unfortunately, experiment and theory suggest that extrinsic disorder in free standing 2D layers disrupts correlation-driven quantum behavior. Here we demonstrate a route to realizing fragile 2D quantum states through endotaxial polytype engineering of van der Waals materials. The true isolation of 2D charge density waves (CDWs) between metallic layers stabilizes commensurate long-range order and lifts the coupling between neighboring CDW layers to restore mirror symmetries via interlayer CDW twinning. The twinned-commensurate charge density wave (tC-CDW) reported herein has a single metal–insulator phase transition at ~350 K as measured structurally and electronically. Fast in-situ transmission electron microscopy and scanned nanobeam diffraction map the formation of tC-CDWs. This work introduces endotaxial polytype engineering of van der Waals materials to access latent 2D ground states distinct from conventional 2D fabrication. Correlated quantum states in free-standing two-dimensional materials are susceptible to defects and thermal disorder. Here, the authors demonstrate two-dimensional ordered charge density wave states above room temperature in clean interleaved polytype heterostructures of a van der Waals material. [ABSTRACT FROM AUTHOR]

[Display omitted] • A type-I band alignment was determined for Y 0.07 Al 0.93 N/GaN heterojunction. • Demonstration of YAlN-based HEMT with remarkable carrier transport properties. • Identification of key factors impacting temperature-dependent transport properties. Incorporating rare earth element scandium (Sc) into III-nitride wurtzite lattice offers remarkable non-oxide ferroelectrics, tunable spontaneous polarization coefficients, and significantly enhanced linear and nonlinear optical properties. Yttrium (Y), a Sc substitute, is also capable of similar properties when alloyed with III-nitride materials, but its potential has remained largely unexplored. In this study, we present the first experimental investigation into the energy band gap alignment and transport properties of a YAlN based high-electron-mobility transistor (HEMT) structure. Our measurements revealed a type-I band alignment for the Y 0.07 Al 0.93 N/GaN heterojunction, with a small valence band offset of −0.1 eV and conduction band offset of 2.2 eV. We then developed a novel Y 0.07 Al 0.93 N/AlN/GaN heterojunction-based HEMT and evaluated its transport properties. A mobility of 1000 cm2/Vs, a sheet electron concentration of 4.2 × 1013 cm2, and a sheet resistance of 148 Ω/□ were measured at room temperature, which are among the best values reported for rare earth element-containing nitride epitaxial heterostructures. We have further performed temperature-dependent Hall measurements and identified the dominant factors affecting transport properties at different temperature ranges. The excellent electrical characteristics and compatibility with mainstream semiconductor technology represent a significant step forward in the development of next-generation multifunctional HEMTs. [ABSTRACT FROM AUTHOR]