Pseudo-easy-axis anisotropy in antiferromagnetic \(S=1\) diamond-lattice systems Ni\(X_{2}\)(pym)\(_{2}\)

We investigate the magnetic properties of \(S=1\) antiferromagnetic diamond lattice, Ni\(X_{2}\)(pyrimidine)\(_{2}\) (\(X\) = Cl, Br), hosting a single-ion anisotropy (SIA) orientation which alternates between neighbouring sites. Through neutron diffraction measurements of the \(X\) = Cl compound, t...

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Published in:arXiv.org 2024-11
Main Authors: Vaidya, S, Hernández-Melián, A, Tidey, J P, Curley, S P M, Sharma, S, Manuel, P, Wang, C, Hannaford, G L, Blundell, S J, Manson, Z E, Manson, J L, Singleton, J, Lancaster, T, Johnson, R D, Goddard, P A
Format: Article
Language:English
Subjects:
Anisotropy
Antiferromagnetism
Broken symmetry
Fields (mathematics)
Magnetic permeability
Magnetic properties
Magnetic saturation
Magnetic structure
Neutron diffraction
Neutrons
Parameter estimation
Phase transitions
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Summary:We investigate the magnetic properties of \(S=1\) antiferromagnetic diamond lattice, Ni\(X_{2}\)(pyrimidine)\(_{2}\) (\(X\) = Cl, Br), hosting a single-ion anisotropy (SIA) orientation which alternates between neighbouring sites. Through neutron diffraction measurements of the \(X\) = Cl compound, the ordered state spins are found to align collinearly along a pseudo-easy-axis, a unique direction created by the intersection of two easy planes. Similarities in the magnetization, exhibiting spin-flop transitions, and the magnetic susceptibility in the two compounds imply that the same magnetic structure and a pseudo-easy-axis is also present for \(X\) = Br. We estimate the Hamiltonian parameters by combining analytical calculations and Monte-Carlo (MC) simulations of the spin-flop and saturation field. The MC simulations also reveal that the spin-flop transition occurs when the applied field is parallel to the pseudo-easy-axis. Contrary to conventional easy-axis systems, there exist field directions perpendicular to the pseudo-easy-axis for which the magnetic saturation is approached asymptotically and no symmetry-breaking phase transition is observed at finite fields.
ISSN:2331-8422
DOI:10.48550/arxiv.2405.15623