Multiple magnetic phases in DyNiAl4

Abstract

Members of the orthorhombic RNiAl4 series of materials are known to display variations in the character and number of ordered magnetic phases dependent on the particular rare earth ion present. In TbNiAl4 there are two ordered phases, the first being an incommensurate elliptical helix type structure [1-3] and the second, lower temperature phase being a commensurate structure with magnetic moments aligned along the a-axis. In PrNiAl4, there are also two magnetic phases with the incommensurate phase in this case consisting of a sinusoidal modulation of the magnetic moment along the easy a-axis [4]. ErNiAl4 only has an incommensurate magnetic phase, with the magnetic moments pointing along the c-axis but sinusoidal in magnitude along the perpendicular a- and b-axes [5]. The magnetic phases generally exist independently of each other for a given compound, though in TbNiAl4 the incommensurate and commensurate phases have been shown to coexist in a decreasing magnetic field [2]. New neutron diffraction data recently obtained for DyNiAl4 using the ECHIDNA High Resolution Powder Diffractometer [6] has not only confirmed two ordered magnetic phases, but that these two phases coexist in the region between the two transition points identified in the specific heat data in zero applied field [7].