Muon spin relaxation and electron/neutron diffraction studies of BaTi2(As1−xSbx)2O: Absence of static magnetism and superlattice reflections

Abstract

We present the results of muon spin relaxation/rotation, transmission electron microscopy, and neutron diffraction measurements performed on several specimens of BaTi${}_{2}$(As${}_{1\ensuremath{-}x}$Sb${}_{x}$)${}_{2}$O, which is known to have either charge density or spin density wave ordering at ${T}_{\mathrm{DW}}$ for all $x$, and superconductivity below ${T}_{\mathrm{c}}$ \ensuremath{\approx} 1 K for $x$ $=$ 1. Zero-field muon spin relaxation measurements show no significant increase in relaxation rate at the density wave ordering temperature for any composition, indicating that the density wave is of the charge rather than spin type. The absence of any superstructure peaks in selected area electron and high-resolution neutron diffraction measurements below ${T}_{\mathrm{DW}}$ suggests that the charge density wave does not involve modulation of atomic arrangement. Transverse field muon spin rotation measurements reveal a robust superconducting state below ${T}_{\mathrm{c}}$ \ensuremath{\approx} 1 K for $x$ $=$ 1.