Dynamic magnetic susceptibility of Gd5Si2Ge2 and Gd4YSi1.9Ge2.1

The effects of diluting Gd with Y on the magnetic properties of the giant magnetocaloric effect material Gd5Si2Ge2 have been investigated by high incident energy inelastic neutron scattering, magnetization, and x-ray powder diffraction measurements. The dynamic response for Gd5Si2Ge2 at 15 and 150 K consists of two magnetic excitations extending up to 40 meV. From the x-ray powder diffraction data, Gd4YSi1.9Ge2.1 is monoclinic at room temperature, space group P112(1)/a with the 4e site at x=-0.0092(3), y=0.1005(2), z=0.1808(4) almost exclusively occupied by Gd (97%), while the remaining four Gd/Y sites are randomly occupied by Gd and Y. The magnetization measurements show that the ordering temperature of Gd4YSi1.9Ge2.1 is about half that of Gd5Si2Ge2, as the former orders ferromagnetically at 149 K with an effective paramagnetic moment of 7.87mu(B). The observed magnetic dynamic response for the Gd4YSi1.9Ge2.1 at 7 K is also different from the nondiluted compound, whereby the positions and intensities of the magnetic excitations have decreased markedly with respect to Gd5Si2Ge2.