Ising exchange interaction in lanthanides and actinides

TL;DR

This paper establishes the precise conditions under which lanthanide and actinide ions exhibit Ising exchange interactions, refining the understanding of magnetic anisotropy and aiding the design of targeted magnetic materials.

Contribution

It provides necessary and sufficient criteria for Ising exchange in lanthanides and actinides, challenging previous assumptions and classifying two types of Ising interactions.

Findings

Narrowed the range of ions capable of Ising exchange.

Identified two types of Ising interactions: coaxial and non-coaxial.

Provided guidelines for designing magnetic materials with specific anisotropy properties.

Abstract

The Ising exchange interaction is a limiting case of strong exchange anisotropy and represents a key property of many magnetic materials. Here we find necessary and sufficient conditions to achieve Ising exchange interaction for metal sites with unquenched orbital moments. Contrary to current views, the rules established here narrow much the range of lanthanide and actinide ions which can exhibit Ising exchange interaction. It is shown that the arising Ising interaction can be of two distinct types: (i) coaxial, with magnetic moments directed along the anisotropy axes on the metal sites and (ii) non-coaxial, with arbitrary orientation of one of magnetic moments. These findings will contribute to purposeful design of lanthanide and actinide based materials.