Jul 13, 2017
Spin-orbit coupling control of anisotropy, ground state and frustration in 5d2 Sr2MgOsO6
Neutron scattering intensity maps, measured with Ei = 20 meV, showing the gap below TN for (a) Sr2MgOsO6 and (b) Sr2ScOsO6 which closes above TN in (c,d) respectively.
The influence of spin-orbit coupling (SOC) on the physical properties of the 5d2 system Sr2MgOsO6 is probed via a combination of magnetometry, specific heat measurements, elastic and inelastic neutron scattering, and density functional theory calculations. Although a significant degree of frustration is expected, we find that Sr2MgOsO6 orders in a type I antiferromagnetic structure at the remarkably high temperature of 108 K. The measurements presented allow for the first accurate quantification of the size of the magnetic moment in a 5d2 system of 0.60 μB –a significantly reduced moment from the expected value for such a system. Furthermore, significant anisotropy is identified via a spin excitation gap, and we confirm by first principles calculations that SOC not only provides the magnetocrystalline anisotropy, but also plays a crucial role in determining both the ground state magnetic order and the size of the local moment in this compound. Through comparison to Sr2ScOsO6, it is demonstrated that SOC-induced anisotropy has the ability to relieve frustration in 5d2 systems relative to their 5d3 counterparts, providing an explanation of the high TN found in Sr2MgOsO6.
R. Morrow, A. E. Taylor, D. J. Singh, J. Xiong, S. Rodan, A. U. B. Wolter, S. Wurmehl,
B. Büchner, M. B. Stone, A. I. Kolesnikov, Adam A. Aczel, A. D. Christianson,
P. M. Woodward
Scientific Reports 6, 32462 (2016)