Tunable polar distortions and magnetism in Gd π₯ β’La 1βπ₯ β’PtSb epitaxial films
Hexagonal π΄β’π΅β’πΆ intermetallics are predicted to have tunable ferroelectric, topological, and magnetic properties as a function of the polar buckling of π΅β’πΆ atomic planes. Here, we report the impact of isovalent lanthanide substitution on the buckling, structural phase transitions, and electronic and magnetic properties of Gd π₯ β’La 1βπ₯ β’PtSb films grown by molecular beam epitaxy (MBE) on π plane sapphire substrates. The Gd π₯ β’La 1βπ₯ β’PtSb films form a solid solution from π₯=0 to π₯=1 and retain the polar hexagonal structure (πβ’6 3 β’πβ’π) out to π₯ β€ 0.95. With increasing π₯, the PtSb buckling increases and the out-of-plane lattice constant π decreases due to the lanthanide contraction. While hexagonal LaPtSb is a highly conductive polar metal, the carrier density decreases with π₯ until an abrupt phase transition to a zero band overlap semimetal is found for cubic GdPtSb at π₯=1. The magnetic susceptibility peaks at small but finite π₯, which we attribute to Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling between localized 4β’π moments, whose concentration increases with π₯, and free carriers that decrease with π₯. Samples with π₯β₯0.3 show antiferromagnetic Curie-Weiss behavior and a Neel temperature that increases with π₯. The Gd π₯ β’La 1βπ₯ β’PtSb system provides opportunities to dramatically alter the polar buckling and concentration of local 4β’π moments.