DIRECT MEASUREMENT OF THE MAGNETOCALORIC EFFECT IN La(Fe_(13-x-y)Co_y)Si_x COMPOUNDS NEAR ROOM TEMPERATURE

摘要

In the last decade magnetic refrigeration principle based on the magnetocaloric effect (MCE) attracted much attention and was a subject of intense studies. Nowadays an increasing interest is given to the LaFe_(13-x)Si_x series of compounds, especially due to potentially high MC properties and low cost. To increase the Curie temperature T_C close to room temperature, many attempts have been devoted to the substitution of Fe or La in LaFe_(13-x)Si_x compounds by either transition metals e.g. Mn, Co, or rare-earth elements e.g. Er, Nd, Ce. Among these elements, Co appears the best-suited element to range T_C close to 300 K. Most of the published papers dedicated to this question aim to report on physical properties of La(Fe,Co)_(13-x)Si_x compounds with data only related to the entropy change. Here we report on the isothermal entropy change and the direct measurement of the temperature change for LaFe_(11.9-y)Co_ySi_(1.1) compounds (x = 1.1 and y = 0.8 and 0.9) around room temperature. Measurements of △T were performed in adiabatic conditions with practice-oriented method by using a specially developed test bench.