Publication Date:
2016-10-15
Description:
Author(s): A. Mannig, J. S. Möller, M. Thede, D. Hüvonen, T. Lancaster, F. Xiao, R. C. Williams, Z. Guguchia, R. Khasanov, E. Morenzoni, and A. Zheludev Magnetic insulators are widely used as prototypes for the study of quantum criticality. Among the more exotic experimental realizations is the z = 1 Heisenberg quantum critical point (QCP). It hosts asymptotic freedom of quasiparticles, unconventional scaling properties, and excitations analogous to the Higgs boson in high-energy physics. An interesting question is how this quantum phase transition is affected by disorder. Theory predicts a destruction of the quantum critical point and the emergence of a quantum Griffiths phase. In the present work, this issue is addressed experimentally by studying one of the precious few materials that host a pressure-induced Heisenberg QCP, namely the organometallic quantum magnet piperazine hexachlorodicuprate (PHCC). Disorder is introduced by chemical substitution of bromine for chlorine on a nonmagnetic site. Magnetic ordering at low temperatures is then studied as a function of applied hydrostatic pressure for a range of impurity concentrations. The tool of choice is the highly sensitive muon-spin rotation technique. The authors uncover a dramatic effect of disorder on the magnetic phase diagram. In agreement with theoretical expectations, they detect strong magnetic inhomogeneities already for small impurity concentrations, followed by the destruction of pressure-induced magnetic order at high concentrations of impurities. [Phys. Rev. B 94, 144418] Published Fri Oct 14, 2016
Keywords:
Magnetism
Print ISSN:
1098-0121
Electronic ISSN:
1095-3795
Topics:
Physics
Permalink