Sommerfeld coefficient enhancement and magnetic short-range order in a hyperkagome 3 system

社本 真一*; 安井 幸夫*; 吉澤 香奈子*; 野田 幸男*; 高橋 美和子*; 大貫 惇睦*; 芳賀 芳範; 石角 元志*; 山内 宏樹; Huang, T.-C.*; et al.

Physical Review B, 113(23), p.235126_1 - 235126_7, 2026/06

https://doi.org/10.1103/m5pw-ghz3

-Mn shows a large Sommerfeld constant of 70 mJ,,Mn,,K, which is one of the largest values in 3-electron systems. Although the origin has been attributed to the fluctuating magnetic moment, there are no material-dependent systematic studies in the 3-electron systems except for doped -Mn. The ordered -Mn structure compounds MnTX (T = Co, Rh, Ir; X = Si, Ge) also exhibit the enhancement. We have studied the enhancement in MnTX system. The enhancement has been often accompanied with magnetic short-range order. The mechanism of the magnetic short-range order is discussed based on the phase diagrams of MnTX system. The phase diagrams are categorized in two groups. One group of MnCoSi and MnRhSi exhibits the magnetic short-range order above the Nel temperature, whereas the others do not. The two groups can be separated by the spin-orbit coupling value, regardless of the cubic lattice parameter.