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  Kraemer, C.; Nikseresht, N.; Piatek, J.O.; Tsyrulin, N.; Dalla Piazza, B.; Kiefer, K.; Klemke, B.; Rosenbaum, T.F.; Aeppli, G.; Gannarelli, C.; Prokes, K.; Podlesnyak, A.; Straessle, T.; Keller, L.; Zaharko, O.; Kraemer, K.W.; Ronnow, H.M.: Dipolar Antiferromagnetism and Quantum Criticality in LiErF₄. Science 336 (2012), p. 1416-1419

10.1126/science.1221878
Open Access version by external provider

Abstract:
Magnetism has been predicted to occur in systems in which dipolar interactions dominate exchange. We present neutron scattering, specific heat, and magnetic susceptibility data for LiErF4, establishing it as a model dipolar-coupled antiferromagnet with planar spin-anisotropy and a quantum phase transition in applied field Hc|| = 4.0 ± 0.1 kilo-oersteds. We discovered non–mean-field critical scaling for the classical phase transition at the antiferromagnetic transition temperature that is consistent with the two-dimensional XY/h4 universality class; in accord with this, the quantum phase transition at Hc exhibits three-dimensional classical behavior. The effective dimensional reduction may be a consequence of the intrinsic frustrated nature of the dipolar interaction, which strengthens the role of fluctuations.