M. Otero-Leal | Searcharxiv

arXiv2008

Identification of a Marginal Fermi-Liquid in Itinerant Ferromagnet CoS2

We report specific heat, resistivity and susceptibility measurements at different temperatures, magnetic fields, and pressures to provide solid evidence of CoS2 being a marginal Fermi liquid. The presence of a tricritical point in the phase diagram of the system provides an opportunity to test the spin fluctuation theory with a high limit of accuracy. A magnetic field suppresses the amplitude of the spin fluctuations and recovers conventional Fermi liquid behavior, connecting both states continuously.

cond-mat.str-el↗

arXiv2005

Suppression of Ferromagnetic Double Exchange by Vibronic Phase Segregation

From Raman spectroscopy, magnetization, and thermal-expansion on the system La2/3(Ca1-xSrx)1/3MnO3, we have been able to provide a quantitative basis for the heterogeneous electronic model for manganites exhibiting colossal magnetoresistance (CMR). We construct a mean-field model that accounts quantitatively for the measured deviation of TC(x) from the TC predicted by de Gennes double exchange in the adiabatic approximation, and predicts the occurrence of a first order transition for a strong coupling regime, in accordance with the experiments. The existence of a temperature interval TC<T<T* where CMR may be found is discussed, in connection with the occurrence of an idealized Griffiths phase.

cond-mat.str-el↗