Magnetoelectricity coupled exchange bias in BaMnF4

Evolution of magnetic phase in two-dimensional van der Waals Mn1-xNixPS3single crystals

Metal thio(seleno)phosphatesMPX₃have attracted considerable attentions with wide spanned band gaps and rich magnetic properties. In this series, two neighboring members MnPS₃and NiPS₃differ in magnetic atoms, magnetic easy axes, spin anisotropy, as well as nearest-neighbor magnetic interactions. The competition between these components may cause intriguing physical phenomena. In this article, the evolution of magnetism of Mn_1-xNi_xPS₃series is reported. Despite the incompatible antiferromagnetic orders of two end members, the antiferromagnetism persists as the ground state in the whole substitution region. The magnetic ordering temperatureT_Nshow nonmonotonic V-shape behavior, and the reentrant spin glass phase atx= 0.5 is observed. In addition, abnormal bifurcation ofT_Noccurs atx= 0.75, which may be due to the temperature-dependent spin reorientation or phase separation. The evolution of magnetism is further confirmed semi-quantitatively by our density functional theory calculations. Our study indicates that exotic magnetism can be intrigued when multi-degrees of freedom are involved in these low-dimensional systems, which call for more in-depth microscopic studies in future.

Multiferroic decorated Fe2O3 monolayer predicted from first principles

Two-dimensional (2D) multiferroics exhibit cross-control capacity between magnetic and electric responses in a reduced spatial domain, making them well suited for next-generation nanoscale devices; however, progress has been slow in developing materials with required characteristic properties. Here we identify by first-principles calculations robust 2D multiferroic behaviors in decorated Fe2O3 monolayers, showcasing Li@Fe2O3 as a prototypical case, where ferroelectricity and ferromagnetism stem from the same origin, namely Fe d-orbital splitting induced by the Jahn-Teller distortion and associated crystal field changes. These findings establish strong material phenomena and elucidate the underlying physics mechanism in a family of truly 2D multiferroics that are highly promising for advanced device applications.

Direct Magnetization-Polarization Coupling in BaCuF_{4}

Herewith, first-principles calculations based on density functional theory are used to describe the ideal magnetization reversal through polarization switching in BaCuF_{4} which, according to our results, could be accomplished close to room temperature. We also show that this ideal coupling is driven by a single soft mode that combines both polarization, and octahedral rotation. The later being directly coupled to the weak ferromagnetism of BaCuF_{4}. This, added to its strong Jahn-Teller distortion and its orbital ordering, makes this material a very appealing prototype for crystals in the ABX_{4} family for multifunctional applications. The described mechanism behaves ideally as it couples the ferroelectric and the magnetic properties naturally and it has not been reported previously.

Crystal Growth, Structure, Resistivity, Magnetic, and Photoelectric Properties of One-Dimensional Selenometallate Ba2 BiFeSe5

Low-dimensional materials have attracted extensive research interest in recent years owing to their interesting structural chemistry and physical properties, which will greatly deepen our knowledge of these materials and could lead to additional breakthroughs in the future. Herein we have synthesized and characterized Ba₂ BiFeSe₅ , which adopts a quasi-one-dimensional structure and possesses some fascinating physical properties. The sharp divergences between the field-cooled (FC) and the zero-field-cooled (ZFC) data and the rather small magnetic moment per Fe³⁺ (0.07 μ_B ) strongly suggest that the title compound is weakly ferromagnetic with a high magnetic transition temperature above room temperature, which is controlled by competing super-exchange interactions within and between [FeBiSe₅ ]_∞ anionic ladders. Moreover, with its narrow bandgap of 0.95 eV, Ba₂ BiFeSe₅ shows photoelectric properties with a photocurrent density of approximately 30 mA cm² at 5 V. Our study demonstrates that Ba₂ FeBiSe₅ might be a new type of multifunctional material that deserves further investigation.

Synthesis, Optical, and Magnetic Properties of Ba2Ni3F10 Nanowires

A low-temperature hydrothermal route has been developed, and pure phase Ba₂Ni₃F₁₀ nanowires have been successfully prepared under optimized conditions. Under the 325 nm excitation, the Ba₂Ni₃F₁₀ nanowires exhibit three emission bands with peak positions locating at 360, 530, and 700 nm, respectively. Combined with the first-principles calculations, the photoluminescence property can be explained by the electron transitions between the t_2g and e_g orbitals. Clear hysteresis loops observed below the temperature of 60 K demonstrates the weak ferromagnetism in Ba₂Ni₃F₁₀ nanowires, which has been attributed to the surface strain of nanowires. Exchange bias with blocking temperature of 55 K has been observed, which originates from the magnetization pinning under the cooling field due to antiferromagnetic core/weak ferromagnetic shell structure of Ba₂Ni₃F₁₀ nanowires.

Strong room-temperature blue-violet photoluminescence of multiferroic BaMnF4

BaMnF4 microsheets have been prepared using a hydrothermal method. Strong room-temperature blue-violet photoluminescence has been observed (an absolute luminescence quantum yield of 67%) with two peaks located at 385 nm and 410 nm. More interestingly, photon self-absorption phenomenon has been observed, leading to an unusual abrupt decrease in the luminescence intensity at a wavelength of 400 nm. To understand the underlying mechanism of such emission, the electronic structure of BaMnF4 has been studied using first principles calculations. The observed two peaks are attributed to electron transitions between the upper-Hubbard bands of the Mn's t2g orbitals and the lower-Hubbard bands of the Mn's eg orbitals. The Mott gap mediated d-d orbital transitions may provide additional degrees of freedom to tune the photon generation and absorption in ferroelectrics.