Neutron scattering in $Er_{2-x}Y_{x}Ti_2O_7$

$Er_2Ti_2O_7$(ETO) is a strong candidate for ground state selection via the order by disorder mechanism. A $\psi_2$ magnetic ground state appears below T$_N$=1.2 K, where $\psi_2$ and $\psi_3$ are the two basis states of the irreducible representation $\Gamma_5$. No sample dependance has been observed in the thermodynamics properties of ETO at low temperature, and in particular on its phase transition to long range magnetic order. ETO's ordered Neel state has been shown to be robust even to a relatively high level of magnetic dilution, as occurs with non-magnetic $Y^{3+}$ substitution of $Er^{3+}$.However, recently two theoretical studies have predicted that ETO's $\psi_2$ ground state should be unstable to formation of the $\psi_3$ state, in the presence of such disorder. To explore this possibility,we grew single crystals of $Er_{2-x}Y_{x}Ti_2O_7$(EYTO) with x = 0,0.2 and 0.4 and performed a systematic inelastic neutron scattering studies using the Disk Chopper time-of-flight spectrometer (DCS) at the National Institute of Standards and Technology (NIST). We will show elastic and inelastic neutron scattering at low temperatures and as a a function of applied magnetic field for all three samples and discuss the role of such quenched disorder on the spin dynamics of EYTO.