Crystal field investigation in the light rare earth R$_3$Pt$_{23}$Si$_{11}$ compounds

TL;DR

This study investigates the crystal electric field in light rare earth compounds, using neutron spectroscopy and advanced optimization to determine CEF parameters, revealing magnetic anisotropy and magnetization behavior in Ce3Pt23Si11.

Contribution

The paper develops a combined genetic algorithm and optimization method to determine unique CEF parameters, providing insights into magnetic anisotropy in Ce3Pt23Si11.

Findings

Unique CEF parameters for Ce3Pt23Si11 were identified.

Strong anisotropy causes an easy threefold magnetization axis.

Magnetization processes are well reproduced by a microscopic model.

Abstract

The crystalline electric field (CEF) is investigated in Pr$_3$Pt$_{23}$Si$_{11}$ and Nd$_3$Pt$_{23}$Si$_{11}$ by neutron spectroscopy (NS). At low temperature, the number of observed CEF excitations is consistent with the orthorhombic symmetry at the rare earth site. This agrees with previous results on Ce$_3$Pt$_{23}$Si$_{11}$. For Pr- and Nd$_3$Pt$_{23}$Si$_{11}$, the number of CEF parameters is too large to allow for an unambiguous determination. This determination is possible for Ce$_3$Pt$_{23}$Si$_{11}$, due to a reduced number of parameters and to the availability of extensive experimental data. A specific procedure is developed for this purpose that combines genetic algorithmics and optimization methods. An unique set of CEF parameters is found for Ce$_3$Pt$_{23}$Si$_{11}$. It reveals a strong anisotropy at the orthorhombic site, responsible for an easy threefold magnetization axis in the cubic system. Using a microscopic, mean-field, description, the magnetization processes in the paramagnetic and ferromagnetic phases of Ce$_3$Pt$_{23}$Si$_{11}$ are well reproduced. Ce$_3$Pt$_{23}$Si$_{11}$ is shown to realize a model for systems where conflicting anisotropies are forced to cooperate.