Magnetic structure of HoPd₂Si₂redefined on the basis of new neutron diffraction data

Abstract

A new sample of HoPd2Si2 (ThCr2Si2-type structure, space group I4/mmm) has been prepared and investigated. Magnetic susceptibility and magnetization data indicate antiferromagnetic behaviour below TN = 5.8 K. On the basis of powder neutron diffraction data the magnetic structure of the compound has been redefined and found to be more complex than reported earlier. In the temperature region from 20 K to 5 K a short-range magnetic order develops. Between 1.5 K and 5 K a long-range magnetic ordering, that could be described in an enlarged magnetic unit cell (am = 7a, bm = a and cm = 6c), is observed. A complex magnetic structure of sine-wave modulated type with two propagation vectors and Ho magnetic moments parallel to the b-axis is proposed. Moreover, a new attempt to understand the transition from long- to short-range magnetic ordering observed in some rare earth compounds with Pd is made.

Neutron diffraction and magnetization studies of pseudoternary HoRh2-xPdxSi2 solid solutions (0$\leq$x<2)

“…Bulk magnetization measurements carried out at 50 and 100 Oe show that HoRh 2−x Pd x Si 2 intermetallics order antiferromagnetically at temperatures lower than 30 K: HoRh 2 Si 2 (figure 1) orders at T N = 28.5 K and then, at T t = 12.6 K, a further magnetic phase transition is visible in the temperature dependence of the magnetization. Substitution of Pd for Rh results in significant lowering of the ordering temperature: all the other intermetallics of the reported series order at about 5 K-that is close to the Néel temperature of HoPd 2 Si 2 (T N = 5.8 K [4]). Magnetic transition temperatures are listed in table 1, in which the crystal and magnetic structure parameters determined by the Rietveld refinements are also collected.…”

“…k x , k z are the components of the propagation vectors of the modulated magnetic structures (in all the cases k y = 0). b As reported in [4].…”

“…To illustrate typical features of neutron diffraction patterns obtained in paramagnetic and magnetically ordered states in this series of solid solutions, some representative pictures are shown in figures 2-5. The neutron diffraction patterns of the parent compounds: HoRh 2 Si 2 (this work) and HoPd 2 Si 2 (after [4]) are shown in figures 2 and 3, respectively. HoRh 2 Si 2 is paramagnetic at 30 K and the scattering by the nucleus gives rise to nuclear Bragg peaks that could be indexed on the basis of the space group I 4/mmm (figure 2(a)).…”

“…HoPd 2 Si 2 was found to belong to the group of materials with mixed magnetic phases where a particular element localized at a unique crystallographic site has two distinct magnetic states: one nonmagnetic and the other with a well-defined magnetic moment. In the case of HoPd 2 Si 2 this leads to the onset of a short-range magnetic ordering in the temperature region 5-20 K followed by a complex magnetic structure of a sine-wave-modulated type with two propagation vectors at lower temperatures [4].…”

Temperature-dependent structure of an intermetallic ErPd2Si2 single crystal: a combined synchrotron and in-house X-ray diffraction study

“…Most of the previous studies on ErPd 2 Si 2 were focused on the low-temperature regime (Yakinthos and Gamari-Seale, 1982; Bażela et al , 1991, 1997; Tomala et al , 1994; Szytuła et al , 2001; Cao et al , 2014; Uchima et al , 2018), and there exist few temperature-dependent studies, especially from the structural point of view. Therefore, we grew the intermetallic ErPd 2 Si 2 single crystals and performed a temperature-dependent structural study up to 500 K. We carried out both in-house X-ray powder diffraction (XRPD) and synchrotron X-ray powder diffraction (SXRPD) measurements on a pulverized ErPd 2 Si 2 single crystal to determine the temperature dependence of the unit-cell parameters and to check the potential structural phase transition.…”