NaCo₂(SeO₃)₂(OH): competing magnetic ground states of a new sawtooth structure with 3d⁷ Co²⁺ ions

Abstract

While certain magnetic sublattices have long been known theoretically to give rise to emergent physics via competing magnetic interactions and quantum effects, finding such configurations in real materials is often...

Field tunable magnetic transitions of CsCo2(MoO4)2(OH): a triangular chain structure with a frustrated geometry

“…Similar higher values have been noticed previously for pseudo-1-D Co 2+ compounds such as SrCo(VO 4 )(OH) (5.4 μ B per Co), 54 Na 4 CoTeO 6 (5.14 μ B per Co) 55 and NaCo 2 (SeO 3 ) 2 (OH) (4.84 μ B per Co). 25 However, it is important to emphasize that at lower temperatures the ground state of distorted octahedral Co 2+ is a Kramers doublet. Therefore, at lower temperatures the magnetic properties of Co 2+ is determined by the lowest Kramers doublet, J = 1/2.…”

“…Additionally, the magnetic structure refinement of NaCo 2 (SeO 3 ) 2 (OH) yield an average of 2.1 μ B per Co, indicating a possible J eff = 1/2 state at lower temperature. 25…”

“…The NaCo 2 (SeO 3 ) 2 (OH) structure is a rare experimental realization of the sawtooth magnetic lattice with two competing magnetic transitions that undergoes a FM transition at 11 K and followed by an AFM transition at 3.8 K. Additionally, NaCo 2 (SeO 3 ) 2 (OH) exhibits a complex field induced magnetic phase diagram. 25 Recently, Rb 2 Mn 3 (MoO 4 ) 3 (OH) 2 was synthesized as single crystals using a high-temperature ( T = 580 °C) hydrothermal method. The compound has a half-delta chain magnetic lattice and exhibits complex magnetism with two consecutive magnetic transitions which include a transition from a paramagnetic to an incommensurate phase below 4.5 K and to a commensurate antiferromagnetic transition below 3.5 K. 24 This wide variety of magnetic ground states in sawtooth chain compounds motivate us to synthesize new materials, and therefore we have continued to explore the MoO 4 2− oxyanion based sawtooth compounds.…”

“…The delta chain (also known as ''sawtooth chains'') and half-delta chain represent special classes of 1-D compounds that possess geometrical frustration. [23][24][25] The quantum nature and spin frustration of such 1-D systems could manifest themselves in the behavior of the elementary excitations. [26][27][28][29][30][31][32][33][34] Structurally speaking, the sawtooth magnetic lattice is made by sharing the corners of triangles alternately pointing up and down in a wave fashion along a 1-D chain.…”

“…In such a scenario the magnetic ground state is determined by the relative strength of J 1 and J 2 , and could lead to exotic magnetically ordered states. [23][24][25] Furthermore, the sawtooth magnetic chains are often interconnected by nonmagnetic spacers such as oxyanion groups (SiO 4 4À , PO 4 3À , AsO 4 3À , VO 4 2À , etc. ), [23][24][25] which serve as paths for possible interchain interactions.…”