The La-excess alloys La1+δ(Fe0.85Si0.15)13 (δ = 0.06 and 0.09) exhibit large magnetocaloric effect which has been attributed to the occurrence of itinerant-electron metamagnetic transition near the Curie temperature TC. The maximum entropy change −ΔSm was shown to be from 4.5 to 11.5 J/kg K for the applied field variation ΔH from 20 to 70 kOe, respectively. The estimated relative cooling power for ΔH = 70 kOe was 418 J/kg. The alloys show a typical NaZn13-type cubic structure, featuring a doping-induced magnetovolume effect with the increase in TC. Under the applied pressure up to 2 GPa, the TC as deduced from resistance measurements decreased linearly, ΔTC = 113 (for δ = 0.06) and 111 K (for δ = 0.09), together with a corresponding decrease of resistivity, Δρ = 6.1 μΩ m at room temperature for both samples. At a low pressure, the effect of spontaneous magnetostriction on TC caused by applying the pressure appeared to have a similar magnitude to that of the negative magnetovolume effect caused by La-excess doping. In comparison with other stoichiometric La(Fe1−xSix)13 compounds, the pressure in our case was shown to have a smaller influence on TC.

Abstract:The TbTSn compounds (T = Pt, Rh) have been prepared by arc-melting in purified Ar atmosphere. Crystal structures were studied by X-ray powder diffraction. The Rietveld analysis shows the single phase in hexagonal ZrNiAl-type structure for TbPtSn and TbRhSn compounds. Magnetic properties and specific heat measured by mean of Physical Properties Measurement System (PPMS) demonstrated the phase magnetic transition at Néel temperature T N .