Random Fields and the Partially Paramagnetic State of CsCo$_{0.83}$Mg$_{0.17}$Br$_{3}$

Partially paramagnetic Neel states are among the exotic magnet states known to exist in nature as a consequence of geometrical frustration. This unusual magnetic structure occurs in the stacked triangular lattice antiferromagnets such as CsCoBr$_{3}$ and CsCoCl$_{3}$. CsCoBr$_{3}$ displays at least 2 magnetic phase transitions. The first, T$_{n1}\sim $28K where the system enters a 3-sublattice state in which on of the sublattices remains disordered and the second, T$_{n2}\sim $13K where the remaining disordered sublattice orders[1]. Critical neutron scattering measurements were performed on the doped system CsCo$_{(1-x)}$Mg$_{(x)}$Br$_{3}$ with x =0.17. We will discuss the evolution of the observed two component scattering below T$_{n1}$ in terms of a Random Field Ising model in both zero applied magnetic field and an applied magnetic field of 2.6T along the c-axis. [1] M.Mao et al. Phys. Rev. B 66, 184432 (2002).