Infrared transmission study of crystal-field excitations in La2-x-yNdxSryCuO4 -: art. no. 224508

We report an infrared crystal field study of La2-x-yNdxSryCuO4 single crystals for (x=0.35, y=0), (x=0.34, y=0.14), and (x=0.42, y=0.19). Nd3+ crystal field excitations from the ground state multiplet I-4(9/2) to the I-4(11/2), I-4(13/2), I-4(15/2), and F-4(3/2) excited multiplets are observed. A precise set of crystal field parameters, that reproduces the Nd3+ electronic levels in all the samples as well as the La1.65Nd0.35CuO4 susceptibility measurements as a function of temperature, is determined. A very strong Ising-like anisotropy of the low-temperature Nd3+ magnetic moment is related to a large value of the second rank crystal field parameter B-20. In addition to the Nd3+ C-4v symmetry regular site a second one, of lower symmetry, is detected and related to possible stripe formation.