Interplay between disorder-driven non-Fermi-liquid behavior and magnetism in the Ce_0.24La_0.76Ge compound

Abstract

In this work, we investigate the magnetic, heat capacity and electrical transport properties of Ce 0.6 La 0.4 Ge and Ce 0.24 La 0.76 Ge compounds. Our results show that two antiferromagnetic transitions (~ at 4.7 and 2.7 K) exhibited by Ce 0.6 La 0.4 Ge are suppressed below 1.8 K for Ce 0.24 La 0.76 Ge. Interestingly, for Ce 0.24 La 0.76 Ge, susceptibility, heat capacity and electrical resistivity vary with temperature as: T 0.75 , T 0.5 and T 1.6 respectively. The observation of such anomalous temperature variation suggests to the Non-Fermi-liquid (NFL) behavior due to the presence of disordered 4f spins due to Ce-site dilution. Under the application of magnetic field, it is noted that a crossover from the NFL to a magnetic state occurs around 2 Tesla, where, short-range correlations among the spins is prevalent due to the dominance of coupling between the magnetic moments via conduction electrons. Magnetoresistance scaling indicates that behavior of disorder driven NFL state is described by the dynamical mean field theory of the spin glass quantum critical point.Introduction: -In the area of research on 4f electron based compounds, a challenge which remains elusive is to understand the physical properties of materials where singular interaction is mediated by soft collective modes. This investigation is important as the obtained results violate the applicability of Fermi-liquid (FL) theory [1-2]. The FL theory forms a basis to understand the electronic properties and according to this theory, electrical resistivity (ρ) varies as the square of temperature (T) and the ratio of heat capacity (C) and temperature i.e. C/T is constant [3][4].However, it has been noted in many 4f electron based compounds that the FL theory breaks down and shows a Non-Fermi-Liquid (NFL) behavior near quantum critical point (QCP). The ρ of such compound shows a linear behavior with T while, T variation of C/T is logarithmic [5][6][7][8].The observation of such NFL behavior might arise due to the presence of soft order parameter fluctuations resulting in singular interactions mediated between electrons [9][10][11]. In some

Coexistence of non-Fermi liquid behavior and biquadratic exchange coupling in La-substituted CeGe: Nonlinear susceptibility and DFT+DMFT study

“…This exponent decreases with decreasing temperature and reaches 1.5 around 3 K. This observed value is not in accordance to the quadrapole picture (a(T) = 4), octapole picture (a(T) = 6), etc. As mentioned earlier, in the zero field limit (H , disorders driven NFL behavior is present in this compound [24]. The variation of linear susceptibility χ 0 (see figure S2 of supplementary information), indicates that there is the presence of local magnetic moments which increases with decreasing temperature.…”

“…Interestingly, in this compound, in the presence of magnetic fields, an anomaly (above 2 (10 4 ) Oe) in heat capacity, is noted over a wide temperature range. The peak got shifted to higher temperatures with increasing fields [24]. Thus, in this compound a changeover from NFL state to a new phase is noted.…”

“…This observation is ascribed to the dominating intersite interactions energy, which impedes the whole screening of magnetic moments. Due to the substitution of La, disorder driven NFL behavior is observed in Ce 0.24 La 0.76 Ge [24]. Interestingly, in this compound, in the presence of magnetic fields, an anomaly (above 2 (10 4 ) Oe) in heat capacity, is noted over a wide temperature range.…”

“…. It can be due to the presence of NFL state [24]. Hence, it can be said that dynamical screening effect is not important in this compound which possibly evades the quasiparticle picture.…”

“…To shed some light on the possible presence of bi-quadratic exchange coupling, associated with NFL behavior, we choose our recently studied Ce 0.24 La 0.76 Ge compound [24].…”