Charge-density-wave orderings in LaAgSb2: An x-ray scattering study

Abstract

X-ray scattering measurements on LaAgSb2 have revealed the onset of charge-density-wave (CDW) modulations associated with anomalies in the resistivity and magnetic susceptibility of this compound. Below the transition temperature of T-1,T-CDW 207 K, a periodic charge and lattice modulation with tau(1) similar to 0.026(2 pi/a) develops along the a direction of the tetragonal structure (a<c). Further lowering of the temperature results in an additional charge-density-wave ordering below T-2,T-CDW= 186 K along the c direction with tau(2) similar to 0.16(2 pi/c). This ordering is associated with a rather weak anomaly in the c-axis resistivity that was previously unnoticed. With decreasing temperature, the wave vector of this second CDW locks into a commensurate value of 1/6 (2 pi/c) at 164 (+/-1) K. The order parameters of tau(1)-CDW and tau(2)-CDW were deduced from the integrated intensities of the (1 - tau(1) 0 7) and (1 0 7 - tau(2)) satellite peaks, respectively, and are in good agreement with the BCS order parameter. The generalized susceptibility was also calculated, revealing enhanced nesting features for the observed modulation wave vectors.