Epitaxial stabilization of thin films of the frustrated Ge-based spinels

Abstract

Frustrated magnets can host numerous exotic many-body quantum and topological phenomena. GeNi 2 O 4 is a three-dimensional S = 1 frustrated magnet with an unusual two-stage transition to the two-dimensional antiferromagnetic ground state, while GeCu 2 O 4 is a high-pressure phase with a strongly tetragonally elongated spinel structure and magnetic lattice formed by S = 1/2CuO 2 linear chains with frustrated interchain exchange interactions and exotic magnetic behavior. Here, we report on the thin-film epitaxial stabilization of these two compounds. The developed growth mode, surface morphology, crystal structure, and copper valence state were characterized by in situ reflection high-energy electron diffraction, atomic force microscopy, x-ray reflectivity, x-ray diffraction, x-ray photoelectron spectroscopy, and resonant x-ray absorption spectroscopy. Our results pave an alternative route to the comprehensive investigation of the puzzling magnetic properties of these compounds and the exploration of emergent features driven by strain.

Controlling the semiconductor–metal transition in Cu-intercalated TiSe2 by applying stress

“…82 For example, a high-pressure polymorph of GeCu 2 O 4 , which is normally stable above 4 GPa, was stabilized in epitaxial films deposited on MgAl 2 O 4 substrates. 83 A reversible semiconductor–metal switching in thin films of Cu x TiSe 2 could be realized, for example, by applying an appropriate compressive stress to a substrate (Fig. 10c).…”

The Renewed Interest on Brunogeierite, GeFe2O4, a Rare Mineral of Germanium: A Review

“…Thus the structure is comprised of alternating mutually perpendicular layers of 1D CuO 2 S = 1/2 chains interconnected via GeO 4 tetrahedra. The 1D nature of magnetic interactions within the S = 1/2 chains is supported by the magnetic susceptibility data that indicate the onset of long-range magnetic ordering at 33 K. Despite the large tetragonal distortion of the pyrochlore sublattice, the magnetic interaction between Cu ions in GeCu 2 O 4 remains frustrated, in analogy to the Cs 2 CuCl 4 case [ 36 ]. Finally, GeNi 2 O 4 has a cubic spinel structure and is a three-dimensional S = 1 frustrated magnet with an unusual two-stage transition to the two-dimensional antiferromagnetic ground state.…”

“…Finally, GeNi 2 O 4 has a cubic spinel structure and is a three-dimensional S = 1 frustrated magnet with an unusual two-stage transition to the two-dimensional antiferromagnetic ground state. The Ni 2+ ions, electronically non-degenerate, indicate that the frustration cannot be relieved via structural distortion driven by the cooperative Jahn-Teller effect, similarly to GFO [ 36 ]. Therefore, for the Ge spinel oxides, having such a wide diversification of magnetic properties, we can foresee application in different fields.…”