Coexisting Ferromagnetic Order and Disorder in a Uniform System of HydroxyhalideCo2(OH)3Cl

Abstract

Order or disorder often exists in a uniform spin system consisting of one kind of magnetic ion. Nevertheless, they rarely coexist in normal conditions. Our thermodynamic and microscopic magnetic studies of Co2(OH)3Cl, a distorted tetrahedral lattice compound with uniform Co2+ spin, demonstrate that the spins located on one corner of the tetrahedron are periodically ordered, but those on the other three are disordered below a ferromagnetic transition at TC=10.5 K. The partial order resembles that of the field-induced "kagomé-ice" state in spin ice pyrochlore compounds. Evidence suggests that a distortion in the tetrahedron is responsible for this partial ferromagnetic order in a zero field.

Magnetic structure of geometrically frustrated compound Co2Cl(OH)3 determined by proton NMR

“…As for Co 2 Cl(OH) 3 , they reported coexistence of ferromagnetic long-range order and random disorder at temperatures below 10.5 K, which is the Curie temperature of this material. The said coexistence was confirmed by measurements of the magnetic susceptibility and the specific heat, and also by neutron diffraction [4]. Putting all their results together, they suggested that this compound is a 3-dimensional geometrically frustrated material like the rare-earth pyrochlore.…”

“…Based on the above considerations, in our calculation we take four quantities of Co 2+ ions as variable parameters: the magnitudes of magnetic moments, m K and m T , and the angles from the c-axis, y K and y T , where the subscripts K and T stand for kagome and triangular, respectively. Through a neutron diffraction experiment, Zheng et al obtained data that the magnitude of magnetic moments of Co 2+ ions was 4.6 m B [4]. However, we takem K and m T separately, because the crystal field could change the magnitude of magnetic moment.…”

“…Rare-earth pyrochlores such as Ho 2 Ti 2 O 7 and Dy 2 Ti 2 O [1,2] are typical examples of magnetically frustrated compounds. Recently, Zheng et al discovered that the transition metal compounds, M 2 Cl(OH) 3 (M ¼ Cu, Mn, Co), have a 3-dimensional geometrically frustrated tetrahedron structure [3,4]. As for Co 2 Cl(OH) 3 , they reported coexistence of ferromagnetic long-range order and random disorder at temperatures below 10.5 K, which is the Curie temperature of this material.…”

Simulation of coexisting ferromagnetic order and disorder of geometrically frustrated Co2Cl(OH)3

“…Zheng et al [3] concluded that the Co spins are anisotropic Ising spins directed to the body center, on the basis of the magnetic entropy value obtained from a temperature dependent specific heat experiment. According to that view, we used an anisotropic Ising spin directed to the body center of a tetrahedron cell as a model for distorted pyrochlore magnet.…”

“…The transition metal compound Co 2 Cl(OH) 3 has the same tetrahedral structure, but is distorted in one direction. With regard to Co 2 Cl(OH) 3 Zheng et al [3] concluded that the magnetic structure at low temperatures contained coexisting ferromagnetic and random spins, according to magnetic susceptibility, specific heat, mSR, and neutron diffraction measurements. Later, Kubo et al [4] and Zenmyo and Tokita [5] investigated the magnetic structure of the compound by NMR experiments, and obtained similar results.…”