Local nuclear and magnetic order in the two-dimensional spin glass <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>PS</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>
J. N. Graham, M. J. Coak, S. Son, E. Suard, J.-G. Park, L. Clark, A. R. Wildes
Abstract
We present a comprehensive study of the short-ranged nuclear and magnetic order in the two-dimensional spin glass, ${\mathrm{Mn}}_{0.5}{\mathrm{Fe}}_{0.5}{\mathrm{PS}}_{3}$. Nuclear neutron scattering data reveal a random distribution of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Fe}}^{2+}$ ions within the honeycomb layers, which gives rise to a spin glass state through inducing competition between neighboring exchange interactions, indicated in magnetic susceptibility data by a cusp at the glass transition, ${T}_{g}=35$ K. Analysis of magnetic diffuse neutron scattering data collected for both single-crystal and polycrystalline samples gives further insight into the origin of the spin glass phase, with spin correlations revealing a mixture of satisfied and unsatisfied correlations between magnetic moments within the honeycomb planes, which can be explained by considering the magnetic structures of the parent compounds, ${\mathrm{MnPS}}_{3}$ and ${\mathrm{FePS}}_{3}$. We found that, on approaching ${T}_{g}$ from above, an ensemble-averaged correlation length of $\ensuremath{\xi}=5.5(6)\phantom{\rule{0.16em}{0ex}}\AA{}$ developed between satisfied correlations, and below ${T}_{g}$, the glassy behavior gave rise to a distance-independent correlation between unsatisfied moments. Correlations between the planes were found to be very weak, which mirrored our observations of rodlike structures parallel to the c* axis in our single-crystal diffraction measurements, confirming the two-dimensional nature of ${\mathrm{Mn}}_{0.5}{\mathrm{Fe}}_{0.5}{\mathrm{PS}}_{3}$.