Magnetocaloric effect and the influence of pressure on magnetic properties of La-excess pseudo-binary alloys La1+δ(Fe0.85Si0.15)13.

The La-excess alloys La_1+δ(Fe_0.85Si_0.15)₁₃ (d=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 T_C. The maximum entropy change -ΔS_m 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 T_C as deduced from resistance measurements decreased linearly, ΔT_C=113 (for δ=0.06) and 111K (for δ=0.09), together with a corresponding decrease of resistivity, Δp=6.1 µΩ m at room temperature for both samples. At a low pressure, the effect of spontaneous magnetostriction on T_C 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(Fe_1-xSi_x)₁₃ compounds, the pressure in our case was shown to have a smaller influence on T_C. [ABSTRACT FROM AUTHOR]