Frustrated quasidoublets without time-reversal symmetry can host highly unconventional magnetic structures with continuously distributed order parameters even in a single-phase crystal. Here, we report the comprehensive thermodynamic and neutron diffraction investigation on the single crystal of TmMgGaO4, which entails non-Kramers Tm 3+ ions arranged on a geometrically perfect triangular lattice. The crystal electric field (CEF) randomness caused by the site-mixing disorder of the nonmagnetic Mg 2+ and Ga 3+ ions, merges two lowest-lying CEF singlets of Tm 3+ into a ground-state (GS) quasidoublet. Well below Tc ∼ 0.7 K, a small fraction of the antiferromagnetically coupled Tm 3+ Ising quasidoublets with small inner gaps condense into two-dimensional (2D) up-up-down magnetic structures with continuously distributed order parameters, and give rise to the columnar magnetic neutron reflections below µ0Hc ∼ 2.6 T, with highly anisotropic correlation lengths, ξ ab ≥ 250a in the triangular plane and ξc < c/12 between the planes. The remaining fraction of the Tm 3+ ions remain nonmagnetic at 0 T and become uniformly polarized by the applied longitudinal field at low temperatures. We argue that the similar model can be generally applied to other compounds of non-Kramers rare-earth ions with correlated GS quasidoublets.

The [001]-oriented Pb(Mg1/3Nb2/3)O3-0.25PbTiO3(PMN-0.25PT) single crystal has been poled by alternating current polarization (ACP). The piezoelectric, dielectric, and electromechanical properties of PMN-0.25PT crystals were investigated with the variations of the electric field, polarization frequency, and cycles. For the piezoelectric performance of the PMN-0.25PT crystal, the optimum ACP condition was obtained under the electric field of 12–18 kV/cm in the frequency range of 20–40 Hz and after 20 cycles. It gives the crystals an increase by 40% from 1220 pC/N to 1730 pC/N in the piezoelectric coefficient compared with traditional direct current polarization. The patterns of the periodic stripe nanodomains under different polarization conditions were revealed by piezoresponse force microscopy. The enhancement of the piezoelectric performance is attributed to the high density of these domain walls. This work indicates that ACP is an effective way to modify the piezoelectric performance of PMN-0.25PT crystals and make it a promising candidate for sensors and transducers.

Efficient anion recognition is of great significance for radioactive 99 TcO 4 − decontamination, but it remains a challenge for traditional sorbents. Herein, we put forward a tactic using soft crystalline cationic material with anion-adaptive dynamics for 99 TcO 4 − sequestration. A cucurbit[8]uril-based supramolecular metal-organic material is produced through a multi-component assembly strategy and used as a sorbent for effective trapping of TcO 4 − . Excellent separation of TcO 4 − /ReO 4 − is demonstrated by fast removal kinetics, good sorption capacity and high distribution coefficient. Remarkably, the most superior selectivity among metal-organic materials reported so far, together with good hydrolytic stability, indicates potential for efficient TcO 4 − removal. The structure incorporating ReO 4 − reveals that the supramolecular framework undergoes adaptive reconstruction facilitating the effective accommodation of TcO 4 − /ReO 4 − . The results highlight opportunities for development of soft anion-adaptive sorbents for highly selective anion decontamination.