Magnetically-diluted two-dimensional CoIIRhIII bimetallic oxalates as quantum spin liquid candidates

Abstract

A quantum spin liquid (QSL) is an elusive state of spin matter characterized by the absence of long-range magnetic order, even at zero temperature, and by the presence of exotic quasiparticle excitations. In spite of their relevance for quantum communication, topological quantum computation and the understanding of strongly correlated systems, like high-temperature superconductors, the unequivocal experimental identification of materials behaving as QSLs remains challenging. Here, we present a novel 2D heterometallic magnetically-diluted oxalate complex meeting all key requirements to become a QSL: a low spin ground state, determined by spin-orbit coupling, a magnetically-frustrated triangular lattice due to the presence of antiferromagnetic correlations , strongly suppressed direct exchange interactions and the presence of equivalent interfering superexchange paths between Co centres. A combination of specific heat and ac magnetic susceptibility measurements in a wide range of frequencies and temperatures show the presence of strong antiferromagnetic correlations concomitant with no signs of magnetic ordering down to 15 milliKelvin. These results show that magnetically diluted oxalates are therefore appealing QSL candidates as well as versatile systems to chemically fine tune key aspects of a QSL, like magnetic frustration and superexchange paths geometries.