Dimer Physics in the Frustrated Cairo Pentagonal Antiferromagnet Bi2Fe4O9

Abstract

The research field of magnetic frustration is dominated by triangle-based lattices but exotic phenomena can also be observed in pentagonal networks. A peculiar noncollinear magnetic order is indeed known to be stabilized in Bi2Fe4O9 materializing a Cairo pentagonal lattice. We present the spin wave excitations in the magnetically ordered state, obtained by inelastic neutron scattering. They reveal an unconventional excited state related to local precession of pairs of spins. The magnetic excitations are then modeled to determine the superexchange interactions for which the frustration is indeed at the origin of the spin arrangement. This analysis unveils a hierarchy in the interactions, leading to a paramagnetic state (close to the Néel temperature) constituted of strongly coupled dimers separated by much less correlated spins. This produces two types of response to an applied magnetic field associated with the two nonequivalent Fe sites, as observed in the magnetization distributions obtained using polarized neutrons.

arXiv commentArticle: 6 pages, 3 figures. Supplemental Material: 10 pages, 10 figures

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Cited by in corpus (7)

• Magnetization process of the S=1/2 Heisenberg antiferromagnet on the floret pentagonal lattice
• Magnetic properties of a spin-1/2 octagonal lattice
• Infrared phonon spectroscopy on the Cairo pentagonal antiferromagnet Bi2Fe4O9: a study through the pressure induced structural transition
• Experimental determination of the magnetic interactions of frustrated Cairo pentagon lattice materials
• Numerical Study of S=1/2 Heisenberg Antiferromagnet on the Floret Pentagonal Lattice
• Collapsing Behavior of the Ferrimagnetic Ground State of the $S=1/2$ Heisenberg Antiferromagnet on the Lieb Lattice due to Frustration
• Refined spin Hamiltonian on the Cairo pentagonal lattice of Bi2Fe4O9