arXiv subjects

Kyle W. Fruhling

Publications and source records attributed to Kyle W. Fruhling.

3 recordsLinked to original sources

arXiv2026

A high-entropy form of $R$Mn$_6$Sn$_6$ with distinct magnetotransport regimes correlated to different magnetic structures

The kagome $R$Mn$_6$Sn$_6$ material family has attracted significant attention as high-temperature metallic magnets with a host of different magnetic orderings and anisotropy. Theoretical studies point to the rare-earth ($R$) as the determining factor for both the direction of magnetic anisotropy and the type of magnetic ordering in a given compound. This motivates studying high-entropy forms of $R$Mn$_6$Sn$_6$ to examine how the interplay of several rare-earth elements leads to different magnetic states in a single crystal. Here, we present a rare-earth mix of Tb, Dy, Ho, Er, Tm, and Lu that produces phase transitions from a paramagnet to an easy-plane ferrimagnet (FiM) below $T_{\text{C}}$ = 380 K, then to a FiM easy-axis state at $T_{\text{SR1}}$ = 207 K, to a canted FiM ground state below $T_{\text{SR2}}$ = 79 K. This behavior is consistent with previously reported high-entropy $R$Mn$_6$Sn$_6$ compounds; however, uniquely, the rare-earth mix studied here exhibits a broad transition from easy-plane to easy-axis anisotropy from 270 K to 170 K, and reveals a nonmonotonic magnetoresistance. Using neutron scattering data, we found that both observations correlate with an incommensurate modulated contribution to the spin state due to competing rare-earth interactions. This magnetoresistive behavior and the correlated spin structures underscore the potential for rare-earth engineering of magnetism.

cond-mat.mtrl-sci↗

arXiv2025

Engineering the Magnetocaloric Effect in Nd$T_4$B

We present a comprehensive study of the magnetocaloric effect (MCE) in the Nd$T_4$B system where $T$ = Fe, Co, and Ni. These compounds are ferromagnetic kagome materials with tunable ordering temperatures, transition width, and magnetic moments depending on the choice of transition metal. Thus, they are good candidates for investigating the MCE. We characterize the MCE using standard metrics and construct ternary phase diagrams as functions of Fe, Co, and Ni concentrations. Using these phase diagrams, we engineer the composition NdFe$_{1.15}$Co$_{0.46}$Ni$_{2.39}$B to maximize the MCE. Interestingly, the Nd$T_4$B system shows a notable entropy change over a wide temperature range ($\sim$10 to 650 K), and particular compositions have notable MCEs spanning hundreds of Kelvin, making this a suitable system to study for technologies used in a wide range of temperatures. In a few cases, we observe a two-peak MCE. These two transitions, releasing comparable entropy, provide an interesting platform to study for applications in multi-stage cooling.

cond-mat.mtrl-sci↗

arXiv2025

Pressure tuning of competing interactions on a honeycomb lattice

Magnetic exchange interactions are mediated via orbital overlaps across chemical bonds. Thus, modifying the bond angles by physical pressure or strain can tune the relative strength of competing interactions. Here we present a remarkable case of such tuning between the Heisenberg (J) and Kitaev (K) exchange, which respectively establish magnetically ordered and spin liquid phases on a honeycomb lattice. We observe a rapid suppression of the Neel temperature (TN) with pressure in Ag3LiRh2O6, a spin-1/2 honeycomb lattice with both J and K couplings. Using a combined analysis of x-ray data and first-principles calculations, we find that pressure modifies the bond angles in a way that increases the |K/J| ratio and thereby suppresses TN. Consistent with this picture, we observe a spontaneous onset of muon spin relaxation (muSR) oscillations below TN at low pressure, whereas in the high-pressure phase, oscillations appear only when T < TN/2. Unlike other candidate Kitaev materials, Ag3LiRh2O6 is tuned toward a quantum critical point by pressure while avoiding a structural dimerization in the relevant pressure range.

cond-mat.str-el↗