Magnetism and magnetocaloric effect of single-crystal Er5Si4under pressure

Abstract

Magnetic and magnetocaloric properties of single crystalline Er5Si4 have been investigated as a function of the applied magnetic field (up to 50 kOe) and the hydrostatic pressure (up to 10 kbar) in the 5-300 K temperature range along the three main crystallographic directions. The magnetization isotherms show a highly anisotropic behaviour with the easy-magnetization direction along the b-axis for the low-pressure monoclinic and high-pressure orthorhombic structures, in good agreement with previous neutron scattering experiments. Below T C the approach to the saturation shows a step-like behaviour when the magnetic field is applied along the hard directions. The steps are sharper as the pressure increases. At constant magnetic field change, increasing the pressure induces a highly anisotropic enhancement of the magnetic entropy change. An enhancement of 20 % is observed along the easy axis b, where the magnetic entropy change is maximum. The different evolution of the magnitude and temperature dependence of the magnetocaloric effect (MCE) along the three crystallographic directions with pressure is discussed.

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

“…Despite the incompleteness transition, pressure studies have found the magnetic transition temperature of the pure O(I) phase, , to be 37.5 K. Similar measurements were also performed for the three crystallographic directions in a single crystal, and both the magnetization and the Δ S M temperature dependence reported a of 35 and 37 K, respectively , which corroborate well with the result obtained above, = 38.5 K. Furthermore, from analyzing the inverse susceptibility (see Fig. a) it is expected that > since > .…”

Effects of pressure on the magnetic-structural and Griffiths-like transitions in Dy5Si3Ge

“…This behavior has already been observed in an Er 5 Si 4 single crystal under pressure. 16 Magnetization has been measured as a function of field at various temperatures in fields up to 50 kOe at selected hydrostatic pressures ranging from 0 to ∼10 kbar (values at low temperature). The dependence of the magnetization isotherms at 5 K on the hydrostatic pressure is illustrated in Fig.…”

“…In this compound the structural and magnetic transitions are reported to be unusually far apart, i.e., they are separated by a temperature difference of ∼200 K. On cooling, this system undergoes a first-order crystallographic phase transition O(I ) → M in the paramagnetic (PM) state at T t ∼ 200-230 K 10,11 and becomes ferromagnetic (FM) at low temperature, T C = 30 K. 10,[12][13][14] Hydrostatic pressure not only induces the O(I) phase at low temperature, but also shifts the high-temperature crystallographic change at a very high rate of dT t /dP ∼ −30 K/kbar. 15,16 This causes both transitions (the high-temperature crystallographic and the low-temperature magnetic ordering) to collapse at high pressures (above 6 kbar), which stabilizes the O(I)-Er 5 Si 4 over the whole temperature range maximizing the magnetocaloric effect at low temperature. 17 Tb 5 Si 2 Ge 2 is another example that exhibits weakly decoupled magnetic and structural transitions.…”

R5T4 Compounds

“…Study of the magnetic properties of single-crystalline Er 5 Si 4 under applied hydrostatic pressure showed that the magnetic behavior is largely anisotropic (Marcano et al, 2012). However, the overall response to the applied pressurethe enhancement of the ferromagnetic interactions due to the formation of the interslab SidSi bonds, manifested as the increase in T C , is seen along all three crystallographic directions.…”

“…At first, Pecharsky et al (2004b) reported that the heat capacity peak associated with this transition slightly shifts to lower temperatures (dT/dH ¼ À0.058 K/kOe) in applied magnetic fields exceeding 40 kOe. The high-temperature PM-O(I) -PM-M transition shifts to lower temperatures with applied hydrostatic pressure at the incredibly high rate of dT s1 /dP ¼ $À30 K/kbar (Magen et al, 2006b;Marcano et al, 2012). 41 and 42.…”