Unusual Magnetism in a d-Electron Compound Fe(OH)Cl: A X–Y Stacked-Triangular Antiferromagnet with Characteristic Double-Bridge Bonding, Unquenched Orbital Moment and Coexisting Spin Fluctuations

Xu Guang Zheng, Md Mahbubur Rahman Bhuiyan, Ichihiro Yamauchi, Masayoshi Fujihala, Kunihisa Sugimoto, Tatsuya Kawae, Toru Ishigaki

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Abstract

Single crystals of triangular-lattice Fe(OH)Cl in orthorhombic structure were synthesized and its magnetism was studied thoroughly using multiple magnetic probes of magnetization, muon spin rotation=relaxation (μSR) and neutron diffraction. Antiferromagnetic transition was found at TN = 13.3 K together with slow dynamics and surprisingly unquenched orbital moments in the paramagnetic state. Residual spin fluctuations coexisting with a long-range order below TN were witnessed in μSR. A coplanar spin structure of propagation vector k ¼ ð0; 0; 0Þ confined within the triangular lattice was revealed by neutron diffraction to have a relatively small frozen moment of 1.96 μB. Ferromagnetic superexchange interactions through a characteristic zig-zag path via ∼90° angled double Fe==O==Fe and double Fe==Cl==Fe bridges counted for this spin arrangement, presenting similarity and contrasting difference to the antiferromagnetic zig-zag path in the S = 1=2 triangular lattice Cu(OH)Cl in monoclinic structure. The obtained value of critical exponent, β = 0.2585(16), in Fe(OD)Cl agrees well with the theoretical value 0.253 ∓ 0.01 in the X–Y frustrated spin model for stacked-triangular antiferromagnet. Experimental evidence all consistently demonstrate the existence of magnetic order with extensive spin fluctuations on a wide range from ∼1 to 10−9–10−12 s. This work presents a unique system for studying geometric frustration on frustrated triangular lattice with unquenched orbital moment.

Original languageEnglish
Article number014704
Journaljournal of the physical society of japan
Volume93
Issue number1
DOIs
Publication statusPublished - Jan 15 2024

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

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