Co(NO3)2 as an inverted umbrella-type chiral noncoplanar ferrimagnet

Abstract

The low-dimensional magnetic systems tend to reveal exotic spin liquid ground states or form peculiar types of long-range order. Among systems of vivid interest are those characterized by the triangular motif in two dimensions. The realization of either ordered or disordered ground state in triangular, honeycomb or kagome lattices is dictated by the competition of exchange interactions, also being sensitive to anisotropy and the spin value of magnetic ions. While the low-spin Heisenberg systems may arrive to a spin liquid long-range entangled quantum state with emergent gauge structures, the high-spin Ising systems may establish the rigid non-collinear structures. Here, we present the case of chiral non-coplanar inverted umbrella-type ferrimagnet formed in cobalt nitrate Co(NO 3 ) 2 below T C = 3 K with the comparable spin and orbital contributions to the total magnetic moment.

Ising-like Magnetism in Quasi-Two-Dimensional Co(NO3)2·2H2O

“…Two water molecules introduced into the crystal structure of Co(NO 3 ) 2 play the role of chemical scissors, cutting the original framework structure into layers coupled through hydrogen bonds. Properties of Co(NO 3 ) 2 ⋅2H 2 O are in sharp contrast with those observed in waterless Co(NO 3 ) 2 [ 22 ]. The behavior of Co(NO 3 ) 2 is of the Heisenberg type, where the frustration of exchange interactions is lifted by the formation of a 120° noncollinear structure.…”

A combination of organic and inorganic cations in the synthesis of transition metal nitrates: preparation and characterization of canted rectangular Ising antiferromagnet (PyH)CsCo2(NO3)6

“…Among these magnets are layered nickel and cobalt nitrates, Ni(NO 3 ) 2 and Co(NO 3 ) 2 , which have a noncollinear umbrella-type ferrimagnetic ground state stemming from purely antiferromagnetic intralayer and interlayer exchange interactions. 4,5 The geometrical pattern of the spin exchange interactions in the nitrosonium copper nitrate, (NO)Cu(NO 3 ) 3 , suggests that it could be a realization of the Nersesyan–Tsvelik model, 6 whose ground state was argued to be either a resonating valence-bond state or a valence-bond crystal. It was found, however, that this system establishes a long-range magnetic order at ultralow temperatures.…”