K₂Ni(SeO₃)₂: A Perfect S = 1 Triangular-Lattice Antiferromagnet with Strong Geometric Frustration and Easy-Plane Anisotropy

Abstract

We synthesized a single crystal of K 2 Ni(SeO 3 ) 2 (S = 1) with an equilateral triangular lattice (space group R-3m). The magnetic susceptibility χ(T) and heat capacity C p (T) show that the compound is antiferromagnetically ordered at T N ≈ 7 K. The Curie−Weiss temperature is about θ CW = −72.41 and −71.83 K when the field is applied along the ab plane (H//ab) and parallel to the c axis (H//c), respectively, indicating a strong geometric frustration (f ≈ 10). Both the χ(T) and M(H) point to the presence of easy-plane anisotropy. Density functional theory (DFT) calculations estimate the intraplane exchange (J/k B = −19.04 K) and the interplane exchange (J′/k B = −0.01 K), proving the excellent two-dimensionality. The 50 T high-field magnetization M(H) at 2 K indicates a sign of 1/3 magnetization plateau. The high-field electron spin resonance demonstrates the antiferromagnetic resonance modes with easy-plane anisotropy, yielding J highly consistent with the DFT result. Thus, K 2 Ni(SeO 3 ) 2 is a perfect triangular-lattice antiferromagnet with strong frustration and easyplane anisotropy.

Analogous Chain Selenite Chlorides Ba2M(SeO3)2Cl2 (M = Cu2+, Ni2+, Co2+, Mn2+) and Pb2Cu(SeO3)2Cl2 with Tunable Spin S: Syntheses and Characterizations

“…Figure a shows the ZFC and FC curves measured from 2 to 40 K under different magnetic fields for compound 3 . As the applied field increased to 7 T from 0.1 T, the peak around 10.8 K shifts to a lower temperature of 7.8 K, confirming that it is the magnetic transition of LRO. − To further confirm the LRO of 3 occurs at low temperature, the temperature-dependent ESR measurement was conducted from 40 to 2 K. As shown in Figure a, a single peak shown at 40 K persists down to 10 K, suggesting the paramagnetic state in 3 above 10 K. Then, additional peaks occurred when temperature decreased to 2 K, indicating an LRO transition below 10 K in 3 . Noting that the LRO shifts to low temperature at a magnetic field of above 0.1 T. However, the long-range order in 3 may still need to be further confirmed by other techniques later including neutron diffraction.…”

2D antiferromagnetic semiconducting FeCN with interesting properties

“…The appearance of competing AFM interactions in the triangular lattice leads to the magnetic fluctuations. 56–58 Considering that the AFM coupling strength ( J 3 ) between the TNN Fe atoms is the weakest, the spin orientations of three Fe atoms in the triangular sublattices follow the stronger J 1 and J 2 , corresponding to the AFM2 configuration.…”

Coexistence of Long-Range Magnetic Order and Magnetic Frustration of a Novel Two-Dimensional S = 1/2 Structure: Na2Cu3(SeO3)4

“…Both of these compounds comprised bulk 3D crystal structures with interesting magnetic properties. The K 2 M(SeO 3 ) 2 , M = Co, Ni series is another interesting addition to the transition metal-based selenite compounds [36,37]. These compounds have a perfect 2D triangular magnetic lattice and display strongly frustrated magnetism.…”