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4f-spin dynamics in La(2-x-y)Sr(x)Nd(y)CuO(4)

M. Roepke·E. Holland-Moritz·B. Buechner·H. Berg·R. E. Lechner·S. Longeville·J. Fitter·R. Kahn·G. Coddens·M. Ferrand
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Abstract

We have performed inelastic magnetic neutron scattering experiments on La(2-x-y)Sr(x)Nd(y)CuO(4) in order to study the Nd 4f-spin dynamics at low energies. In all samples we find at high temperatures a quasielastic line (Lorentzian) with a line width which decreases on lowering the temperature. The temperature dependence of the quasielastic line width Gamma/2(T) can be explained with an Orbach-process, i.e. a relaxation via the coupling between crystal field excitations and phonons. At low temperatures the Nd-4f magnetic response S(Q,omega) correlates with the electronic properties of the CuO(2)-layers. In the insulator La(2-y)Nd(y)CuO(4) the quasielastic line vanishes below 80 K and an inelastic excitation occurs. This directly indicates the splitting of the Nd3+ ground state Kramers doublet due to the static antiferromagnetic order of the Cu moments. In La(1.7-x)Sr(x)Nd(0.3)CuO(4) with x = 0.12, 0.15 and La(1.4-x)Sr(x)Nd(0.6)CuO(4) with x = 0.1, 0.12, 0.15, 0.18 superconductivity is strongly suppressed. In these compounds we observe a temperature independent broad quasielastic line of Gaussian shape below T about 30 K. This suggests a distribution of various internal fields on different Nd sites and is interpreted in the frame of the stripe model. In La(1.8-y)Sr(0.2)Nd(y)CuO(4) (y = 0.3, 0.6) such a quasielastic broadening is not observed even at lowest temperature.

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M. Roepke, E. Holland-Moritz, B. Buechner, H. Berg, R. E. Lechner, S. Longeville, J. Fitter, R. Kahn, G. Coddens, M. Ferrand. 1999-08-23. 4f-spin dynamics in La(2-x-y)Sr(x)Nd(y)CuO(4). https://doi.org/10.1103/physrevb.60.9793

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