Infrared transmission study of crystal-field excitations in La2-x-yNdxSryCuO4

We report an infrared crystal field study of La 2 - x - y Nd x Sr y CuO 4 single crystals for (x=0.35, y=0), (x =0.34, y=0.14), and (x=0.42, y=0.19). Nd 3 + crystal field excitations from the ground state multiplet 4 I 9 / 2 to the 4 I 1 1 / 2 , 4 I 1 3 / 2 , 4 I 1 5 / 2 , and 4 F 3 / 2 excited multiplets are observed. A precise set of crystal field parameters, that reproduces the Nd 3 + electronic levels in all the samples as well as the La 1 . 6 5 Nd 0 . 3 5 CuO 4 susceptibility measurements as a function of temperature, is determined. A very strong Ising-like anisotropy of the low-temperature Nd 3 + magnetic moment is related to a large value of the second rank crystal field parameter B 2 0 . In addition to the Nd 3 + C 4 v symmetry regular site a second one, of lower symmetry, is detected and related to possible stripe formation.