Muon spin relaxation studies of the frustrated quasi-two-dimensional square-lattice spin systemCu(Cl,Br)La(Nb,Ta)2O7: Evolution from spin-gap to antiferromagnetic state Academic Article uri icon

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abstract

  • We report muon spin relaxation ($\mu$SR) and magnetic susceptibility measurements on Cu(Cl,Br)La(Nb,Ta)$_{2}$O$_{7}$, which demonstrate: (a) the absence of static magnetism in (CuCl)LaNb$_{2}$O$_{7}$ down to 15 mK confirming a spin-gapped ground state; (b) phase separation between partial volumes with a spin-gap and static magnetism in (CuCl)La(Nb,Ta)$_{2}$O$_{7}$; (c) history-dependent magnetization in the (Nb,Ta) and (Cl,Br) substitution systems; (d) a uniform long-range collinear antiferromagnetic state in (CuBr)LaNb$_{2}$O$_{7}$; and (e) a decrease of N\'eel temperature with decreasing Br concentration $x$ in Cu(Cl$_{1-x}$Br$_{x}$)LaNb$_{2}$O$_{7}$ with no change in the ordered Cu moment size for $0.33 \leq x \leq 1$. Together with several other $\mu$SR studies of quantum phase transitions in geometrically-frustrated spin systems, the present results reveal that the evolution from a spin-gap to a magnetically ordered state is often associated with phase separation and/or a first order phase transition.

authors

  • Uemura, YJ
  • Aczel, AA
  • Ajiro, Y
  • Carlo, JP
  • Goko, T
  • Goldfeld, DA
  • Kitada, A
  • Luke, Graeme
  • MacDougall, GJ
  • Mihailescu, IG
  • Rodriguez, JA
  • Russo, PL
  • Tsujimoto, Y
  • Wiebe, Christopher
  • Williams, TJ
  • Yamamoto, T
  • Yoshimura, K
  • Kageyama, H

publication date

  • November 1, 2009