Crystalline electric field of Ce in trigonal symmetry: CeIr3Ge7 as a model case

TL;DR

This paper derives an analytic solution for the crystalline electric field (CEF) of Ce3+ in trigonal symmetry, applies it to CeIr3Ge7, and shows its relevance to similar compounds, revealing strong anisotropy and large level splittings.

Contribution

It provides the first analytic solution for the CEF of Ce3+ in trigonal symmetry and applies it to analyze CeIr3Ge7 and related compounds, clarifying their magnetic properties.

Findings

CeIr3Ge7 has large CEF splittings of 374 K and 1398 K.

The CEF scheme explains strong easy-plane anisotropy.

Similar CEF behavior is observed in CeCd3As3, CeAuSn, and CePdAl4Ge2.

Abstract

The crystalline electric field (CEF) of Ce3+ in trigonal symmetry has recently become of some relevance, for instance, in the search of frustrated magnetic systems. Fortunately, it is one of the CEF case in which a manageable analytic solution can be obtained. Here, we present this solution for the general case, and use this result to determine the CEF scheme of the new compound CeIr3Ge7 with the help of T-dependent susceptibility and isothermal magnetization measurements. The resulting CEF parameters B20 = 34.4 K, B40 = 0.82 K and B43 = 67.3 K correspond to an exceptional large CEF splittings of the first and second excited levels, 374 K and 1398 K, and a large mixing between the +-|5/2> and the -+|1/2> states. This indicates a very strong easy plane anisotropy with an unusual small c-axis moment. Using the same general expressions, we show that the properties of the recently reported system CeCd3As3 can also be described by a similar CEF scheme, providing a much simpler explanation for its magnetic properties than the initial proposal. Moreover, a similar strong easy plane anisotropy has also been reported for the two compounds CeAuSn and CePdAl4Ge2, indicating that the CEF scheme elaborated here for CeIr3Ge7 corresponds to an exemplary case for Ce3+ in trigonal symmetry.