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arXiv · 1310.1023

Criticality in a disordered quantum antiferromagnet by neutron diffraction

E. Wulf·D. Huvonen·J. -W. Kim·A. Paduan-Filho·E. Ressouche·S. Gvasaliya·V. Zapf·A. Zheludev
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Abstract

Field-induced magnetic ordering in the structurally disordered quantum magnets Ni(Cl$_{1-x}$Br$_x$)$_2$$\cdot$4SC(NH$_2$)$_2$, $x=8$% and 13%, is studied by means of neutron diffraction. The order parameter critical exponent is found to be very close to its value $β=0.5$ expected for magnetic Bose-Einstein condensation in the absence of disorder. This result applies to temperatures down to 40 mK, and a 1 T range in magnetic field. The crossover exponent is found to be $ϕ\sim 0.4$, for temperature ranges as small as 300 mK. Possible reasons for a discrepancy with recent numerical simulations and bulk measurements are discussed.

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E. Wulf, D. Huvonen, J. -W. Kim, A. Paduan-Filho, E. Ressouche, S. Gvasaliya, V. Zapf, A. Zheludev. 2013-10-03. Criticality in a disordered quantum antiferromagnet by neutron diffraction. https://doi.org/10.1103/physrevb.88.174418

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