Magnetic and structural properties of single-crystalline Er5Si4

Abstract

The magnetization of the oriented Er 5 Si 4 single crystal, measured along the three principal crystallographic directions reveals strong magnetocrystalline anisotropy. The b-axis is the easy magnetization direction. The possible presence of the crystal field effect and the non-collinear alignment of magnetic moments result in a lower than gJ magnetization along all crystallographic directions even in70 kOe applied magnetic field, with the lowest moment (4.22 μ B /Er 3+ ) recorded along the a axis. The magnetization measurements show that even in the true paramagnetic state there is a weak magnetic field dependence of the structural-only transition when the field is applied along the a and c axes but this transition is magnetic field independent along the b-axis in fields of 70 kOe or less. The temperature and magnetic field dependent x-ray powder diffraction study of the powdered single crystal confirms the temperature driven structural orthorhombic -monoclinic transition in the paramagnetic state and the low temperature magnetic field driven monoclinic -orthorhombic transition in the magnetically ordered state. The x-ray powder diffraction indicates that the high temperature transition is magnetic field 2 independent below 40 kOe in a polycrystalline sample while the low temperature transition requires high magnetic field for its completion.

R5T4 Compounds

“…Despite the nonmagnetic character of this transition, it can be seen as a step in the temperature dependence of magnetization, especially when the inverse dc susceptibility (H/M) is plotted. sign along the c-axis (Dc/c ¼ À0.4%) and a minor change of lattice dimensions along the b-axis (Db/b ¼ 0.23%), as determined by Mudryk et al (2012). The temperature dependence of heat capacity of this structural-only transition is manifested as a broad D-type peak with a width of $30 K. The magnetic ordering in Er 5 Si 4 occurs at T C ¼ 30 K, is a typical second-order transition, and is not coupled with a structural transformation.…”

“…The presence of the "high-temperature" 6 O(I) to M structural transition in Er 5 Si 4 during cooling was first reported by Pecharsky et al (2003e); the structural and thermodynamic details of this transition including an established twin law for the monoclinic deformation were carefully investigated by Mozharivskyj et al (2004), and the structural transition in the polycrystalline Er 5 Si 4 was studied by Mudryk et al (2012). Despite the nonmagnetic character of this transition, it can be seen as a step in the temperature dependence of magnetization, especially when the inverse dc susceptibility (H/M) is plotted.…”

“…The study of the Gd 5 Si x Ge 4Àx system and discovery of other rare earth-based systems with 5:4 stoichiometries substantially changed the status quo. Several brief reviews containing information about both chemistry and physics of these extraordinarily interesting compounds have been already published Mudryk et al, 2011;Gschneidner, 2005, 2007), but a comprehensive review covering most of the available science of these materials is lacking. Among those are colossal magnetostriction, spontaneous generation of voltage, pressure enhancement of magnetocaloric effect, unconventional magnetic glass state, spin-flop transition, magnetic deflagration, short-range order magnetic correlations (Griffiths-like phase), and this list is incomplete since science of the R 5 T 4 materials remains an active field.…”

On the nature of the (de)coupling of the magnetostructural transition in Er5 Si4

“…Even though the results obtained for each structure are comparable, the obtained saturation magnetization is of 96.25 emu g -1 , which is approximately half of the experimental value, 200 emu g -1 [4,23,24]. The magnetic moments for the Er atoms, despite being dependent on the sphere radius, are approximately 3µB instead of the 8µB obtained experimentally [8,15].…”