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Static and Dynamic XY-Like Short-Range Order in a Frustrated Magnet with Exchange Disorder



K. A. Ross, J. W. Krizan, Jose Rodriguez Rivera, R. J. Cava, Collin L. Broholm


A single crystal of NaCaCo2Fd7^ was studied using elastic and inelastic neutron scattering. NaCaCo2F7 is a newly synthesized A2B2X7 type pyrochlore, hosting magnetic Co2+ ions on the Bsite and mixed non-magnetic Na+/Ca2+ ions on the a A-site. Fluctuating magnetic correlations are present at temperatures well below the antiferromagnetic interaction strength (θCW=-140 K). the Q-dependence of the inelastic intensity indicates local XY-like antiferromagnetic clusters at energies below 2.5 meV, and fluctuating collinear antiferromagnetic clusters above this energy. Below the freezing transition at Τf=2.4 K, diffuse elastic scattering develops that is consistent with short range XY antiferromagnetism with a correlation length of 16A. The relevant XY states arise from a continuously deformable manifold of states. Contrary to well-known models that produce the same continuous manifold, order-by-disorder does not select an ordered state in NaCCo3F7. Instead, we argue that the weak exchange disorder expected to arise from the heterovalant A-site causes the spin system to freeze into short range ordered clusters that explore this manifold spatially and dynamically on long time scales.
Physical Review B


Neutron Scattering, Sping Liquids, Magnetic materials, Quantum Criticallity


Ross, K. , Krizan, J. , Rodriguez Rivera, J. , Cava, R. and Broholm, C. (2016), Static and Dynamic XY-Like Short-Range Order in a Frustrated Magnet with Exchange Disorder, Physical Review B, [online], (Accessed May 21, 2024)


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Created January 21, 2016, Updated October 12, 2021