arXiv subjects

Jackson Davis

Publications and source records attributed to Jackson Davis.

4 recordsLinked to original sources

arXiv2026

Raman scattering spectroscopic observation of a ferroelastic crossover in bond-frustrated PrCd$_3$P$_3$

2D magnetism in triangular lattices has already shown potential for hosting exotic magnetic states. Control of these magnetic states, both in terms of magnetic properties and in terms of charge doping would be the next step. This makes materials which combine triangular lattice magnetic layers with layers hosting interesting structural or electronic properties particularly useful. PrCd$_3$P$_3$, studied in this work, is one of a family of materials where triangular lattice layers of magnetic rare earth ions alternate with semiconducting hexagonal CdP layers. Using Raman scattering spectroscopy we uncover a structural instability in the CdP layers, associated with a soft mode behavior of a phonon in these layers. Raman scattering detects crystal electric field excitations, and confirms a singlet ground state for Pr$^{3+}$ and splitting of the doublet levels as a result of the structural instability in CdP layers. While Pr$^{3+}$ is non-magnetic in PrCd$_3$P$_3$ we speculate that this family of materials can realize control of the magnetic layer through the CdP layer which can become ferroelectric under strain that would relieve frustration.

cond-mat.mtrl-sci↗

arXiv2024

Tunable magnetism of Boron Imidazolate-based Metal-Organic Frameworks

Magnetic metal-organic frameworks (MMOFs), where magnetic metal nodes are connected into a crystal structure by organic linkers, have a potential to host exotic magnetic states. We present a study of bulk magnetic properties of four metal-organic frameworks with the same boron imidazolate linkers, Cu-BIF, Co-BIF, Ni-BIF, and newly synthesized Zn-BIF, displaying a variety of lattice structures and nontrivial magnetic behaviors. While non-magnetic Zn-BIF provides an offset of magnetic response, magnetic susceptibility measurements of the other three magnetic materials demonstrate the presence of weak magnetic interactions in these MOFs, which differ between materials by sign and size. Cu-BIF, where magnetic nodes are connected into octahedral cages, shows simple paramagnetic behavior. Triangular lattice Co-MOF shows antiferromagnetic interactions on the order of 1 K, and a spin-crossover-like effect in magnetic susceptibility due to thermal depopulation of excited crystal electric field levels. Magnetic properties of Ni-BIF suggest sizable ferromagnetic interactions. Using DC/AC susceptibility and variable-field DC magnetization, we detect cluster spin-glass behavior in Ni-BIF and discuss possible microscopic origins of this behavior. This work demonstrates the variety of magnetic properties that are possible with a single organic ligand, and establishes the low energy scale of magnetic interactions through superexchange in boron imidazolate frameworks.

cond-mat.mtrl-sci↗

arXiv2023

Raman Scattering Spectra of Boron Imidazolate Frameworks Containing Different Magnetic Ions

We present a Raman scattering spectroscopic study of boron imidazolate metal-organic frameworks (BIFs) with three different magnetic metal ions and one non-magnetic in a wide frequency range from 25 to 1700 cm$^{-1}$, which covers local vibrations of the linkers and well as collective lattice vibrations. We show that the spectral region above 800 cm$^{-1}$ belongs to the local vibrations of the linkers, which have the same frequencies for the studied BIFs without any dependence on the structure of the BIFs, and are easily interpreted based on the spectra of imidazolate linkers. In contrast, collective lattice vibrations, observed below 100 cm$^{-1}$, show a distinction between cage and two-dimensional BIFs structures, with a weak dependence on the metal node. We identify the range of vibrations around 200 cm$^{-1}$, which are distinct for each MOF, depending on a metal node. Our work demonstrates the energy hierarchy in the vibrational response of BIFs.

cond-mat.mtrl-sci↗

arXiv2022

Hydrothermal synthesis of ordered corkite, PbFe3(PO4)(SO4)(OH)6, a S = 5/2 kagom\'e antiferromagnet

Corkite, PbFe3(PO4)(SO4)(OH)6, an understudied relative of the jarosite family of Heisenberg antiferromagnets, has been synthesized and its magnetic properties characterized for the first time. Relative to natural samples, synthetic corkite displays signatures in both infrared and Raman spectra of a more ordered arrangement of polyanion groups about the kagom\'e sublattice that retains inversion symmetry. Magnetic susceptibility measurements reveal that dried corkite undergoes a transition to a long-range, antiferromagnetically-ordered state below TN = 48 K, lower than that observed in the majority of jarosite phases, and indicative of further spin frustration. Curie-Weiss fitting of the measured magnetic susceptibility yields an effective magnetic moment of peff = 6.29(1) muB/Fe^3+ and theta_CW = -526.0(1.1) K, analogous to that observed in similar high-spin Fe^3+ systems, and indicative of strong antiferromagnetic coupling. Estimation of the change in magnetic entropy as a function of temperature from T = 0 K to T = 195 K, dS_mag = 14.86 J/mol_Fe^3+ K, is also in good agreement with the dS_mag = Rln(2S+1) = 14.9 J/mol K expected for a S = 5/2 system. In comparison to the pure jarosites, where both structure and magnetism remain largely invariant upon a variety of chemical substitutions, the replacement of one sulfate group per formula unit with a higher-valent phosphate group applies additional steric and electronic pressure on the kagom\'e lattice in corkite, further frustrating the magnetic ground state of the material. Corkite thus represents both an outlier in the known body of jarosite-type materials, and an illustration of how existing structures may be further strained in the development of highly frustrated magnetic systems.

cond-mat.str-el↗