Elastocaloric measurements of the ferroquadrupolar/nematic rare-earth intermetallic TmAg₂ are presented. TmAg₂ undergoes a cooperative Jahn-Teller-like ferroquadrupolar phase transition at 5K, in which the Tm³⁺ ion’s local 4f electronic ground state doublet spontaneously splits and develops an electric quadrupole moment which breaks the rotational symmetry of the tetragonal lattice. The elastocaloric effect, which is the temperature change in the sample induced by adiabatic strains the sample experiences, is sensitive to quadrupolar fluctuations in the paranematic phase which couple to the induced strain. We show that elastocaloric measurements of this material reveal a Curie-Weiss like nematic susceptibility with a Weiss temperature of T* ≈ 2.7K, in agreement with previous elastic constant measurements. Furthermore, we establish that a magnetic field along the c-axis acts as an effective transverse field for the quadrupole moments.

介绍了铁四极/向列稀土金属间化合物 TmAg ₂ 的弹热测量。 TmAg ₂ 在 5K 时经历协同 Jahn-Teller 式铁四极相变，其中 Tm ³⁺ 离子的局部 4f 电子基态双峰自发分裂并产生电四极矩，该四极矩断裂四方晶格的旋转对称性。弹热效应是由样品经历的绝热应变引起的样品温度变化，它对与引起的应变耦合的副相中的四极涨落敏感。我们表明，这种材料的弹性热测量揭示了类居里-魏斯向列磁化率，魏斯温度为 T* ≈ 2.7K，与之前的弹性常数测量结果一致。此外，我们确定沿 c 轴的磁场充当四极矩的有效横向场。