Investigation of the Magnetic Properties in the Pyrochlore Pr$_{2}$Sn$_{2}$O$_{7}$*

Pyrochloric compounds are best known for their remarkable magnetic properties, particularly the possibility to generate magnetic monopoles excitations at low temperatures. Compared to the A$^{3+}$ ions in the spin ice compounds A$_{2}$Ti$_{2}$O$_{7}$ (where A = Ho or Dy), the Pr$^{3+}$ ions in Pr$_{2}$Sn$_{2}$O$_{7}$ have a smaller magnetic moment (2.6 $\mu_{B}$/Pr [1]). This ultimately leads to quantum fluctuations that suppress the spins' ability to freeze [2]. AC susceptibility measurements were performed on a polycrystalline Pr$_{2}$Sn$_{2}$O$_{7}$ sample to probe its dynamic ground state for temperatures down to 11 mK. Preliminary results indicate a narrow distribution of relaxation rates which, as evidenced by neutron experiments [3], are governed by quantum tunneling between states. In addition, relaxation times extracted from isothermal frequency sweeps were found, within error, to be temperature independent below 1 K. Future measurements include specific heat from which the field-dependence of the magnetic monopole densities may be extracted.\\[4pt] [1] K. Matsuhira et al., J. Phys. Soc. Jpn. \textbf{71}, 1576 (2002)\\[0pt] [2] S. Onoda et al., PRL \textbf{105}, 047201 (2010)\\[0pt] [3] H.D. Zhou et al., PRL \textbf{101}, 227204 (2008)