Spin glassiness and power law scaling in anisotropic triangular spin-1/2 antiferromagnets

Department of Physics and Center for Materials Innovation, Washington University - St. Louis, MO 63136, USA

^a Seidel@physics.wustl.edu

Received: 13 January 2011
Accepted: 15 February 2011

Abstract

We present data on the magnetic properties of two classes of layered spin S = 1/2 antiferromagnetic quasi-triangular lattice materials: Cu_2(1−x)Zn_2x(OH)₃NO₃(0 ≤ x ≤ 0.65) and its long-organic-chain–intercalated derivatives Cu_2(1−x)Zn_2x(OH)₃(C₇H₁₅COO)·mH₂O(0 ≤ x ≤ 0.29), where non-magnetic Zn substitutes for Cu isostructurally. It is found that the intercalated compounds, even in a clean system in the absence of dilution, x=0, show spin glass behaviour, as evidenced by DC and AC susceptibility, and by time-dependent magnetization measurements. A striking feature is the observation of a sharp crossover between two successive power law regimes in the DC susceptibility above the freezing temperature. In constrast to standard theoretical expectations, these power laws are insensitive to doping. Specific heat data are consistent with a conventional phase transition in the unintercalated compounds, and glassy behaviour in the intercalated compounds.