Evidence of Ferroelectric Distortions in Topological Crystalline Insulators via Transverse Thermoelectric Measurements.

The transverse thermoelectric (Nernst) effect is a powerful probe for studying the electronic and structural properties of materials. In this study, we employ transverse thermoelectric measurements to investigate the ferroelectric distortion in the topological crystalline insulator (TCI) PbSnTe, a compound derived from PbTe and SnTe, known for their exceptional thermoelectric performance and distinct ferroelectric properties. By leveraging Nernst measurements, we provide direct evidence of ferroelectric distortion in this TCI, corroborated by Shubnikov-de Haas quantum oscillations that confirm the presence of two topologically nontrivial Fermi pockets.

Giant Topological Hall Effect and Colossal Magnetoresistance in Heusler Ferromagnet near Room Temperature.

Colossal magnetoresistance (CMR) is an exotic phenomenon that allows for the efficient magnetic control of electrical resistivity and has attracted significant attention in condensed matter due to its potential for memory and spintronic applications. Heusler alloys are the subject of considerable interest in this context due to the electronic properties that result from the nontrivial band topology. Here, the observation of CMR near room temperature is reported in the shape memory Heusler alloy NiMnIn, which is attributed to the combined effects of magnetic field-induced martensite twin variant reorientation (MFIR) and magnetic field-induced structural phase transformation (MFIPT).

Contrasting Magnetic Characteristics of Disordered NdBaMnFeO and 112-Type Ordered NdBaMnFeO Perovskites.

The magnetic properties of disordered NdBaMnFeO and ordered NdBaMnFeO perovskites were investigated through temperature- and field-dependent DC-magnetization measurements. The temperature dependence of magnetic susceptibilities revealed that antiferromagnetic ordering occurs at temperatures below 185 K for the disordered NdBaMnFeO sample, whereas the ordered NdBaMnFeO perovskite exhibited a paramagnetic state throughout the entire temperature range examined. Notably, the disordered sample exhibited a glassy state, even at room temperature, which transformed into an antiferromagnetic state under higher applied magnetic fields.

Giant Room-Temperature Topological Hall Effect in a Square-Net Ferromagnet LaMnGe.

A topological magnetic material showcases a multitude of intriguing properties resulting from the compelling interplay between topology and magnetism. These include notable phenomena such as a large anomalous Nernst effect (ANE), an anomalous Hall effect (AHE), and a topological Hall effect (THE). In most cases, topological transport phenomena are prevalent at temperatures considerably lower than room temperature, presenting a challenge for practical applications.

High-pressure synthesis and magnetic properties of tetragonal BaCuO ( = Sm and Eu).

We report the experimental discovery of a new structural phase of well-known orthorhombic BaCuO ( = Sm and Eu), exhibiting a tetragonal crystal structure with space group . The high-pressure tetragonal phase is isostructural with the brown phase BaCuO ( = La, Pr, and Nd). In this structure, the Cu ions form an isolated square planar environment, contrary to the orthorhombic phase, where the Cu ions are located in a distorted square pyramid.

Interplay between Magnetism and Topology: Large Topological Hall Effect in an Antiferromagnetic Topological Insulator, EuCuAs.

Magnetic interactions in combination with nontrivial band structures can give rise to several exotic physical properties such as a large anomalous Hall effect, the anomalous Nernst effect, and the topological Hall effect (THE). Antiferromagnetic (AFM) materials exhibit the THE due to the presence of nontrivial spin structures. EuCuAs crystallizes in a hexagonal structure with an AFM ground state (Néel temperature ∼ 16 K).

Raman Evidence of Multiple Adsorption Sites and Structural Transformation in ZIF-4.

The zeolitic imidazolate framework, ZIF-4, exhibits soft porosity and is known to show pore volume changes with temperatures, pressures, and guest adsorption. However, the mechanism and adsorption behavior of ZIF-4 are not completely understood. In this work, we report an open to narrow pore transition in ZIF-4 around ∼ 253 K upon lowering the temperature under vacuum (10 Torr) conditions, facilitated by C-H···π interactions.