High-field magnetization and electronic spin resonance study in the twisted honeycomb lattice α -Mn 2 V 2 O 7 .

We report the single-crystal growth of Mn ₂ V ₂ O ₇ and the results of magnetic susceptibility, high-field magnetization up to 55 T and high-frequency electric spin resonance (ESR) measurements for its low-temperature α phase. Two antiferromagnetic (AFM) ordering at 17.5 K and 3 K and obvious magnetic anisotropy are observed in α -Mn ₂ V ₂ O ₇ upon cooling. In pulsed high magnetic fields, the compound reaches the saturation magnetic moment of ∼10.5 μ _B for each molecular formula at around 45 T after two undergoing AFM phase transitions at H _c1 ≈ 16 T, H _c2 ≈ 34.5 T for H //[11-0] and H _sf1 = 2.5 T, H _sf2 = 7 T for H //[001]. In these two directions, two and seven resonance modes are detected by ESR spectroscopy, respectively. The ω ₁ and ω ₂ modes of H //[11-0] can be well described by two-sublattice AFM resonance mode with two zero-field gaps at 94.51 GHz and 169.28 GHz, indicating a hard-axis feature. The seven modes for H //[001] are partially separated by the critical fields of H _sf1 and H _sf2 , displaying the two signs of spin-flop transition. The fittings of ω _c1 and ω _c2 modes yield zero-field gaps at 69.50 GHz and 84.73 GHz for H //[001], confirming the axis-type anisotropy. The saturated moment and gyromagnetic ratio indicate the Mn ²⁺ ion in α -Mn ₂ V ₂ O ₇ is in a high spin state with orbital moment completely quenched. A quasi-one-dimensional magnetism with a zig-zag-chain spin configuration is suggested in α -Mn ₂ V ₂ O ₇ , due to the special neighbor interactions caused by a distorted network structure with honeycomb layer.
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