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When exploring low dimensional coordination polymers, their specific magnetic properties are of particular interest to confirm their dimensionality and calculate their exchange energy (J). While Cu(pym)2(NO3)2 is already a known compound, the magnetic qualities of it remained unconfirmed. This sample of Cu(pym)2(NO3)2 was synthesized in a 1:1 ratio of Cu(NO3)2 and pyrimidine in water. Well structured, blue crystals were produced andbrought to the Mag Lab at Los Alamos National Laboratory (LANL) for pulsed field magnetic research. Utilizing their 65T magnet, pulsing this sample at 60T revealed a concave saturation graph, further confirming the known structure as a 1D coordination polymer. From this data, the specific saturation points of different temperatures—0.5K and 1.5K—and different orientations of the magnetic field—orthogonal and parallel—were extracted. The pulsed field magnetic research indicates that Cu(pym)2(NO3)2 is indeed a 1D coordination polymer, with average exchange energies of 38.214K in an orthogonal magnetic field and 41.312K in a parallel magnetic field. 

Developing materials with tunable magnetic properties remains a significant challenge. Our efforts in materials science include the design and synthesis of innovative magnet structures using molecular building blocks. This poster presents the synthesis of the compound Cu(SO4)(2- aminopyrimidine)2(H2O)2, and efforts to identify and verify the composition and geometry of a metal complex using infrared spectroscopy and single-crystal X-ray diffraction. Recent results from high magnetic field measurements will also be presented. 

Chirality in magnetic systems gives rise to a wide range of exotic phenomena, yet its influence in S = 1 chains remains largely unexplored. Here, we present a comprehensive experimental study of a chiral antiferromagnetic (AFM) S = 1 chain, [Ni(pym)(H2O)4]SO4· H2O (pym = pyrimidine), where the Ni(II) octahedral orientation exhibits a four-fold chiral periodicity. Muon spin rotation measurements indicate the onset of long-range magnetic order below TN = 1.82(2) K. Neutron diffraction measurements reveal a chiral AFM order driven by a chiral modulation of the easy-axis anisotropy direction, rather than the typical scenario of Dzyaloshinskii-Moriya interactions, geometrical frustration or higher-order interactions. Inelastic neutron scattering (INS) measurements reveal dispersive spin-wave excitations well described by linear spin-wave theory, with Hamiltonian parameters J0 = 6.81(1)K (intrachain exchange), J′ 1a = −0.091(1)K (interchain exchange), and D = −3.02(1)K (easy-axis single-ion anisotropy). These parameters are further validated by Monte Carlo simulations of the magnetisation. Additionally, the INS data reveal multiple dispersionless bands, suggesting the presence of further excitations beyond the scope of linear spin-wave theory. 

Materials composed of spin-1 antiferromagnetic (AFM) chains are known to adopt complex ground states that are sensitive to the single-ion-anisotropy (SIA) energy ( $D$ ), and intrachain ( $J_0$ ) and interchain ( $J_{1,2}^{\prime }$ ) exchange energy scales. While theoretical and experimental studies have extended this model to include various other energy scales, the effect of the lack of a common SIA axis is not well explored. Here we investigate the magnetic properties of $\mathrm{Ni}\left(\mathrm{pyrimidine}\right){\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left({\mathrm{NO}}_3\right)}_2$ , a chain compound where the tilting of Ni octahedra leads to a twofold alternation of the easy-axis directions along the chain. Muon-spin relaxation measurements indicate a transition to long-range order at $T_{\text{N}}=2.3\mathrm{K}$ and the magnetic structure is initially determined to be antiferromagnetic and collinear using elastic neutron diffraction experiments. Inelastic neutron scattering measurements were used to find $J_0=5.107\left(7\right)\mathrm{K}, D=2.79\left(1\right)\mathrm{K},J_1^{\prime }=0.00\left(5\right)\mathrm{K}, J_2^{\prime }=0.18\left(3\right)\mathrm{K}$ , and a rhombic anisotropy energy $E=0.19\left(9\right)\mathrm{K}$ . Mean-field modeling reveals that the ground state structure hosts spin canting of $\varphi \approx 6.5^{\circ }$ , which is not detectable above the noise floor of the elastic neutron diffraction data. Monte Carlo simulation of the powder-averaged magnetization, $M\left(H\right)$ , is then used to confirm these Hamiltonian parameters, while single-crystal $M\left(H\right)$ simulations provide insight into features observed in the data. Published by the American Physical Society2025 

We investigate the magnetic properties of $S=1$ antiferromagnetic diamond-lattice, $\mathrm{Ni}{X}_2{\left(\mathrm{pyrimidine}\right)}_2$ $(X=\mathrm{Cl}, \mathrm{Br})$ , hosting a single-ion anisotropy (SIA) orientation which alternates between neighboring sites. Through neutron diffraction measurements of the $X=\mathrm{Cl}$ 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 $X=\mathrm{Br}$ . 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. Published by the American Physical Society2024 

Abstract CeOs 4 Sb 12 , a member of the skutterudite family, has an unusual semimetallic low-temperature L -phase that inhabits a wedge-like area of the field H —temperature T phase diagram. We have conducted measurements of electrical transport and megahertz conductivity on CeOs 4 Sb 12 single crystals under pressures of up to 3 GPa and in high magnetic fields of up to 41 T to investigate the influence of pressure on the different H – T phase boundaries. While the high-temperature valence transition between the metallic H -phase and the L -phase is shifted to higher T by pressures of the order of 1 GPa, we observed only a marginal suppression of the S -phase that is found below 1 K for pressures of up to 1.91 GPa. High-field quantum oscillations have been observed for pressures up to 3.0 GPa and the Fermi surface of the high-field side of the H -phase is found to show a surprising decrease in size with increasing pressure, implying a change in electronic structure rather than a mere contraction of lattice parameters. We evaluate the field-dependence of the effective masses for different pressures and also reflect on the sample dependence of some of the properties of CeOs 4 Sb 12 which appears to be limited to the low-field region. 

Using time-domain terahertz spectroscopy in pulsed magnetic fields up to 31 T, we measure the terahertz optical conductivity in an optimally doped thin film of the high-temperature superconducting cuprate La1.84⁢Sr0.16⁢CuO4. We observe systematic changes in the circularly polarized complex optical conductivity that are consistent with cyclotron absorption of 𝑝-type charge carriers characterized by a cyclotron mass of 4.9⁢𝑚e±0.8⁢𝑚e and a scattering rate that increases with magnetic field. These results open the door to studies aimed at characterizing the degree to which electron-electron interactions influence carrier masses in cuprate superconductors.