Frustrated magnetic structure of Y-substituted CePdAl studied by powder neutron diffraction

Abstract

CePdAl is a heavy-fermion antiferromagnet with TN = 2.7 K, crystallizing in the ZrNiAl-type structure. The magnetic structure is described by the propagation vector k = (1/2, 0, τ), τ = 0.35, with the cerium magnetic moments aligned along the c-axis. One third of magnetic moments remains disordered due to the geometrical frustration. Specific heat measurements on substituted Ce1−xYxPdAl compounds revealed strong reduction of TN with Y substitution and the antiferromagnetic order vanishes around x = 0.2. To investigate the microscopic details of the changes in the magnetic structure evoked by nonmagnetic ion substitution, we have performed an experiment on the powder neutron diffractometer E6 at HZB on the samples with x = 0.02, 0.06 and 0.1. Measurements showed the magnitude reduction of the ordered cerium moments with Y substitution while the propagation vector and other magnetic structure characteristics remain unchanged.