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

TL;DR

This study investigates Nd 4f-spin dynamics in La(2-x-y)Sr(x)Nd(y)CuO(4) using neutron scattering, revealing temperature-dependent relaxation processes, effects of magnetic order, and stripe-related phenomena in different doping regimes.

Contribution

It provides new insights into Nd 4f-spin relaxation mechanisms and their relation to electronic properties and stripe order in cuprate superconductors.

Findings

Quasielastic line width decreases with temperature, explained by an Orbach process.

Static antiferromagnetic order causes Nd ground state splitting and inelastic excitations.

Stripe model explains the temperature-independent broad quasielastic line in certain doping levels.

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.