%0 Journal Article
%T Criticality in a disordered quantum antiferromagnet by neutron diffraction
%A E. Wulf
%A D. Huvonen
%A J. -W. Kim
%A A. Paduan-Filho
%A E. Ressouche
%A S. Gvasaliya
%A V. Zapf
%A A. Zheludev
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevB.88.174418
%X 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 $\beta=0.5$ 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 $\phi \sim 0.4$, for temperature ranges as small as 300 mK. Possible reasons for a discrepancy with recent numerical simulations and bulk measurements are discussed.
%U http://arxiv.org/abs/1310.1023v1