Coupling Between 3d and 4f Spin Sublattices in LaNiO$$_3$$-Based Heterostructures

Throughout this chapter, parts of which are based on Bluschke et al. Phys. Rev. Lett. 118, 207203 (2017) [52], we explore the concept of combining two magnetic systems in an epitaxial relationship, with the goal of producing novel magnetic structures with properties inherited from both of the constituent materials. In this study we choose two complementary systems. The first, antiferromagnetic LaNiO\(_3\), hosts a closed shell A-site cation and the strongly correlated nickel and oxygen bands support strong superexchange interactions amongst the Ni spins. The second material, DyScO\(_3\), hosts a closed shell B-site cation and a large, strongly localized magnetic moment of about 9 \(\mu _B\) on the rare-earth Dy\(^{3+}\) site. In contrast to the Ni magnetism of the LaNiO\(_3\) layers, the Dy spins experience weak mutual exchange fields and, instead, a rather strong magneto-crystalline anisotropy associated with the reduced symmetry of their local crystal field environment. The resulting structure, when these two systems are integrated, hosts strong antiferromagnetic correlations on the Ni sites with an anisotropy which is adopted from the nearby Dy ions. As a test case we compared our study of the coupled LaNiO\(_3\)-DyScO\(_3\) system with the closely related system LaNiO\(_3\)-GdScO\(_3\). By replacing Dy with Gd we allow the antiferromagnetic Ni spins to couple to a large rare-earth moment, similar to Dy, but without an additional coupling to the lattice, i.e. no magneto-crystalline anisotropy. These \(\text {LaNiO}_{3}\)-based heterostructures constitute a new and insightful model system for the interaction between 3d and 4f magnetic moments.