Abstract
Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics.
Highlights
The lack of spatial inversion symmetry can stabilize asymmetric exchange interactions in systems with unpaired electrons, giving rise to novel physical phenomena such as multiferroics and topological spin textures [1,2,3,4,5,6]
We developed a method for synthesizing single crystals and bulk-polycrystalline samples of β-Ni(IO3 )2 that exhibit NCS polar structure with integer spin S = 1
Studies in polar magnetic materials possessing asymmetric exchange interactions, which are relevant to possible emergence of topological spin physics, have been in a rather confined space of half-integer spins attributed to the scarcity of integer spin systems with broken spatial inversion symmetry. β-Ni(IO3 )2 was selected for the focus of this work due to its combined integer spin S = 1 and NCS polar lattice components
Summary
The lack of spatial inversion symmetry can stabilize asymmetric exchange interactions in systems with unpaired electrons, giving rise to novel physical phenomena such as multiferroics and topological spin textures [1,2,3,4,5,6]. Increased asymmetric exchange interactions in polar magnets with half-integer spins such as Cu2 OSeO3 (Cu2+ , d9 , 2 D), Fe(IO3 ) (Fe3+ , d5 , 6 S), and VOSe2 O5 (V4+ , d1 , 2 D) have been demonstrated [2,16,17]; studies in integer spin systems featuring the DM interaction have been left unexplored. This is, in part, because there are relatively few integer spin magnets to investigate that have NCS polar lattice symmetries.
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