We examined the piezomagnetic effect in an antiferromagnet MnTe, which is a candidate material for altermagnetism with a high critical temperature. We observed that the magnetization develops with the application of stress and revealed that the piezomagnetic coefficient $Q$ is $1.38\times {10}^{-8}$ ${\mu }_{\mathrm{B}}$/Mn/MPa at 300 K. The poling-field dependence of magnetization indicates that the antiferromagnetic domain can be controlled using the piezomagnetic effect. We demonstrate that piezomagnetic effect is one of the suitable methods for the detection of broken time-reversal symmetry and the domain control in antiferromagnets with broken time-reversal symmetry, including altermagnets.

The pressure effects on the antiferromagentic orders in iron-based ladder compounds ${\text{CsFe}}_2{\mathrm{Se}}_3$ and ${\text{BaFe}}_2{\mathrm{S}}_3$ have been studied using neutron diffraction. With identical crystal structure and similar magnetic structures, the two compounds exhibit highly contrasting magnetic behaviors under moderate external pressures. In ${\text{CsFe}}_2{\mathrm{Se}}_3$ the ladders are brought much closer to each other by pressure, but the stripe-type magnetic order shows no observable change. In contrast, the stripe order in ${\text{BaFe}}_2{\mathrm{S}}_3$ undergoes a quantum phase transition where an abrupt increase of Néel temperature by more than 50% occurs at about 1 GPa, accompanied by a jump in the ordered moment. With its spin structure unchanged, ${\text{BaFe}}_2{\mathrm{S}}_3$ enters an enhanced magnetic phase that bears the characteristics of an orbital selective Mott phase, which is the true neighbor of superconductivity emerging at higher pressures.

The hydrostatic pressure effect on multiferroic properties of rare-earth manganites $R\mathrm{Mn}{\mathrm{O}}_3$ ($R=\mathrm{Dy},\mathrm{Tb}$, and $\mathrm{Gd}$) with the $Pbnm$ orthorhombic structure was investigated by using a diamond anvil cell. Under high pressure, all of these manganites were found to exhibit ferroelectricity in which spontaneous polarization $(\approx {10}^0\mu \mathrm{C}/\mathrm{c}{\mathrm{m}}^2)$ develops along the $a$ axis. The application of a magnetic field $B$ along the $a$ axis to the high-pressure ferroelectric phase causes a drastic change in the electric polarization $P$. Especially in $\mathrm{GdMn}{\mathrm{O}}_3$, the $B$-induced change in $P$ reached $\Delta P\left(B\right)=1.3\mu \mathrm{C}/\mathrm{c}{\mathrm{m}}^2$. A possible origin of the observed $R$-dependent pressure effect is discussed.

The electronic structure of ${\mathrm{BaFe}}_2{X}_3$ ($X$ = S and Se) and ${\mathrm{CsFe}}_2{\mathrm{Se}}_3$ in which two-leg ladders are formed by the Fe sites are studied by means of x-ray absorption and resonant inelastic x-ray scattering spectroscopy. The x-ray absorption spectra at the Fe $L$ edges for ${\mathrm{BaFe}}_2{X}_3$ exhibit two components, indicating that itinerant and localized Fe $3d$ sites coexist. Substantial x-ray linear dichroism is observed in polarization dependent spectra, indicating the existence of orbital order or fluctuation in the Fe ladder even above the Néel temperature $T_{\mathrm{N}}$. Direct exchange interaction along the legs of the Fe ladder stabilizes the orbital and antiferromagnetic orders in ${\mathrm{BaFe}}_2{\mathrm{S}}_3$, while the ferromagnetic molecular orbitals are realized between the rungs in ${\mathrm{CsFe}}_2{\mathrm{Se}}_3$.

A polymorph of RuI3 synthesized under high pressure was found to have a two-layered honeycomb structure. The resistivity of RuI3 exhibited semimetallic behavior, in contrast to the insulating prope...