A MAGNETIC-X-RAY DIFFRACTION INVESTIGATION OF GADOLINIUM SELENIDE

A single-crystal synchrotron radiation study of gadolinium selenide ha s been made in the temperature range 15-100 K. GdSe has the rocksalt s tructure and becomes antiferromagnetic below a reported Neel temperatu re of 65 K. At 15 K, magnetic reflections are observed at G + tau with modulation wavevector tau = {1/2, 1/2, 1/2} propagating from reciproc al lattice point G. This is achieved by exploiting the resonant enhanc ement in the vicinity of the Gd LII and LIII edges. Similar enhancemen ts are observed at the two edges, with the maximum effect occurring ap proximately 3 eV above the absorption edge. The temperature dependence of the intensity of the magnetic reflections indicates a Neel tempera ture of 63(1) K. These measurements, together with high-resolution stu dies of the fundamental reflections (tau = 0), contribute further evid ence of magnetic or structural changes in the sample at 37(1) K. Our o bservations are discussed and compared with previous x-ray diffraction and magnetic susceptibility measurements.