Fases de líquido cuántico de espín en nuevos materiales moleculares

Speca, Chiara
Luis, Fernando (dir.)

Universidad de Zaragoza, CIEN, 2024

Máster Universitario en Física y Tecnologías Físicas

Resumen: The goal of this work has been to experimentally characterize, through magnetization and heat capacity measurements, two novel molecular materials, (PNP)ZnRu(ox)3 and FeCpRhZn(ox)3, in order to understand if they could be two good candidates for Quantum Spin Liquids. The guideline that we followed during our research can be summarized in three key points: the absence of long-range magnetic order, the presence of spin-spin interaction and the compatibility of experimental parameters with the Kitaev-Heisenberg Model. By measuring the temperature dependence of the magnetic susceptibility, we verified the absence of long-range magnetic order down to 360 mK for both materials. This conclusion is supported by the absence of sharp peaks or discontinuities in the temperature dependence of the heat capacity. Still, the same results, supported by heat capacity data, suggest the presence of antiferromagnetic interactions. However, the interactions are also very weak, thus it is still not surprising that the two systems remain paramagnetic even down to 350 mK. By studying the temperature dependence of the experimental heat capacity at zero field, we found that its behavior is consistent with the Kitaev-Heisenberg model predictions, in particular with the existance of spin excitations different from spin flips. The results obtained so far appear promising and are they are compatible with a QSL physics. They need to be extended to very low T, so that the thermal excitation energy is smaller than the scale of spin-spin interactions.

Tipo de Trabajo Académico: Trabajo Fin de Master