Advanced Physics Research最新文献

Anisotropic ferromagnetism within antiferromagnetic crystals

The cover feature showcases the emergence of hard anisotropic ferromagnetism following the intercalation of nonmagnetic pyridinium ions into antiferromagnetic FePS₃ single crystals. In article number 202400101, Yunbo Ou, Feng Liu, Seth Ariel Tongay, and colleagues report the transition from antiferromagnetism to ferromagnetism in pyridinium-intercalated FePS₃, thereby highlighting both the energetically stable B-phase and metastable P-phase. These phases exhibit remarkable properties, including giant coercive fields exceeding 7 T and high Curie temperatures (72–87 K). As revealed by X-ray photoelectron spectroscopy and supported by first-principles calculations and atomistic spin dynamics simulations, electron transfer from the pyridinium ions to FePS₃ plays a key role in driving this transition. This work offers crucial insights into hard magnetism in intercalated van der Waals materials, thus paving the way for advances in 2D magnet-based technologies.

Superconducting nanowires

In article number 2400133, Markus Arndt and co-workers show superconducting nanowires to be a powerful tool for detecting the impact of neutral metastable atoms and neutral molecules at low energy. They achieve remarkable detection efficiencies, responding sensitively to internal electronic energies as low as 11.6 eV and impact energies as small as 3 eV. Their performance in detecting neutral molecules exceeds that of channel electron multipliers by more than 106, opening new opportunities for measurements in atomic and molecular beam physics.

Room-temperature ferromagnetism in diluted magnetic semiconductors

Diluted magnetic semiconductors (DMS), which combine the advantages of carrier processes in semiconductors and spin storage in ferromagnets, have significant impacts on generating brand new information technologies. However, achieving room-temperature ferromagnetism in a controllable mode for DMS is a major challenge. In article number 2400124, Bo Gu, Zheng Deng, Changqing Jin and co-workers report experimental enhancement of T_C to a record 260 K for the new-generation DMS material (Ba,K)(Zn,Mn)₂As₂ (or “BZA”) through high-pressure synthesis that effectively optimizes spin and charge doping.

In the past decade, miniaturized mechanical antennas have become a research focus. Several types of mechanical antennas based on different operation principles, including mechanical antennas based on magnetoelectric effect, mechanical antennas based on permanent magnets, mechanical antennas based on electrets, and mechanical antennas based on piezoelectric resonators, are presented, all with sizes significantly smaller than conventional electrical antennas operating at the same resonant frequencies. This review focuses on the advances in mechanical antennas, potential applications as well as challenges and potential future directions for further performance improvement. Although the sizes of the state-of-the-art mechanical antennas are several orders of magnitude smaller than traditional electrical counterparts with the same resonant frequencies, the reported maximum operation distance of mechanical antennas is still short, which is a major challenge for it to be widely implemented. By adopting new materials for mechanical antennas, adopting array configurations, adopting receiving antennas with higher sensitivity, and building new electromagnetic-electromechanical coupled simulation methods, the maximum operation distance may be significantly improved, making mechanical antennas widely implemented in the Internet of Things (IoT), wireless sensor networks (WSN), implantable medical devices (IMD), and portable electronics applications.

The simple phase diagram of pure VO₂ consisting of an insulating monoclinic M1 phase and a metallic tetragonal R phase with a steep insulator-metal-transition (IMT) at TIMT = 340 K, is enriched by two additional insulating phases, a triclinic (T) and a monoclinic (M2) and multiple phase transitions, when strained or doped with M3⁺ions (M = Ga, Al, Cr, Fe, Mg). Under low-current R(T) measurements, the T(M1 → M2) and IMT are the only once detected by X-ray diffraction that show reproducible resistive switching (RS) and hysteresis typical of first-order transitions. Following the surprising detection of the RS associated with the M1→T transition induced by a high electric field in Ga-, Al-, and Cr-doped VO₂ crystals, we attempted to uncover those associated with additional transitions in Al-doped VO₂ nanostructures, as reported by Strelcov et al., Nano Letters 2012. Reported herein is the investigation of a single crystal of nominal Al_0.01V_0.99O₂ composition, by repeated direct current (DC) and pulsed IV measurements at fixed ambient temperatures below and at room temperature (RT). RS associated with the various phase transitions appeared in the nonlinear I(V) regime induced by self-heating (Joule heating), including all those that are absent under low-electric-current measurements.

Superconducting nanowires are widely recognized as exceptional sensors in photonics, information processing, and astronomy. Even a single infrared photon can break Cooper pairs, generate a hot spot and trigger a measurable quantum phase transition. Here, it is demonstrated that this detection capability is far more versatile. Ultrathin nanowires are shown to be sensitive to the internal energy of atoms as well as to the kinetic energy of neutral molecules, here within the energy range of 10–20 and 3–6 eV, respectively. Superconducting nanowires achieve higher detection quantum yields than channel electron multipliers in the detection of metastable atoms and they surpass the efficiency of secondary electron detectors by more than a factor of 10⁶ in the detection of molecules at impact energies below 5 eV. This remarkable sensitivity paves the way for new applications in atomic and molecular beam physics, establishing nanowires as a crucial tool for future precision measurements.

Atomic Force Lithography

The study 2400108 by Dmitry Yakovlev and co-workers introduces a novel approach to using atomic force microscopy (AFM) pulse force nanolithography to fabricate Bi₂Se₃ nanoribbons with high precision. This allows control over their dimensions and prevents contamination from standard electron beam lithography or reactive ion etching. The illustration shows a pie of complex multilayer heterostructures cut into small pieces by using atomic force lithography with an accuracy of a few nanometers. The results also reveal insights into electronic structure, conductance, and phase coherence in TIs, with thermal excitation and bias current affecting coherence length. This new AFM technique offers a scalable and precise approach.