Spin wave spectra of single crystal CoPS3

Abstract

The spin waves in single crystals of the layered van der Waals antiferromagnet CoPS 3 have been measured using inelastic neutron scattering. The data show four distinct spin wave branches with large ( 14 meV) energy gaps at the Brillouin zone center indicating significant anisotropy. The data were modeled using linear spin wave theory derived from a Heisenberg Hamiltonian. Exchange interactions up to the third nearest-neighbor in the layered planes were required to fit the data with ferromagnetic J 1 = −1.37 meV between first neighbors, antiferromagnetic J 3 = 3.0 meV between third neighbors, and a very small J 2 = 0.09 meV between second neighbors. A biaxial single-ion anisotropy was required, with a collinear term D x = −0.77 meV for the axis parallel to the aligned moment direction and a coplanar term D z = 6.07 meV for an axis approximately normal to the layered crystal planes.

Kinetic and Thermodynamic Pathways Via Ion Exchange Metathesis of Cobalt Thiophosphate

“…The temperature-dependent magnetic susceptibility (Figure a) of the solid solution series shows increasing paramagnetic behavior at lower temperatures and a higher CoCl 2 /MgPS 3 ratio. The results for our metathesis sample are similar to those made via reactive flux method. , The previously discussed P–P disorder likely causes the absence of long-range AFM order by interrupting the exchange interaction pathways observed in the ordered honeycomb sublattice. ,, Long-range AFM order can also be absent due to site disorder and vacancies on the metal site, which are known to produce short-range order in metal-depleted clustering. Another major contributor to cationic disorder is the presence of Mg 2+ cations, as discussed previously.…”

“…The μ eff in Table , indicates that the magnetic moment of Co 2+ is in the high-spin configuration ( S = 3/2), with some unquenched orbital contributions of L ≈ 1. However, neutron diffraction experiments have observed an excess moment, which is argued to originate from an isotropic g factor exceeding the value of 2 . In the case of the 0.7 ratio, the effective magnetic moment indicates that the orbital contribution is quenched, revealing a cobalt–magnesium occupation dependence of the spin–orbit coupling.…”

“…The degree of disorder previously discussed may also present further complexities in the magnetic properties, as the exchange pathways arguably play an important role in CoPS 3 . For example, direct exchange between the metal centers weakens or strengthens depending on the distance of the metal ions. ,, …”

“…For example, direct exchange between the metal centers weakens or strengthens depending on the distance of the metal ions. 27,47,62 The μ eff in Table 3, indicates that the magnetic moment of Co 2+ is in the high-spin configuration (S = 3/2), with some unquenched orbital contributions of L ≈ 1. However, neutron diffraction experiments have observed an excess moment, 31 which is argued to originate from an isotropic g factor exceeding the value of 2.…”

“…35,46 The previously discussed P−P disorder likely causes the absence of long-range AFM order by interrupting the exchange interaction pathways observed in the ordered honeycomb sublattice. 31,45,47 Long-range AFM order can also be absent due to site disorder 48 and vacancies on the metal site, 22 which are known to produce short-range order in metaldepleted clustering. Another major contributor to cationic disorder is the presence of Mg 2+ cations, as discussed previously.…”