一级相变磁制冷材料LaFe_(11.6)Si_(1.4)合金的磁相变特性系统分析

System Analysis of Magnetic Phase Transition Characteristics in the First-Order Magnetic Refrigeration Material of La Fe_(11.6)Si_(1.4) Alloys

以La Fe11.6Si1.4合金为研究对象,系统分析了该一级相变材料的居里温度(TC)、磁场诱导磁相变的临界磁场(HC)、磁化率(χ)、磁滞、磁熵变(ΔS)、制冷能力(RCP)等磁性特性。结果表明:温度诱导磁相变的居里温度和磁场诱导磁相变的临界磁场均随磁场呈线性增加,ΔTC和ΔH随磁场和温度的变化率的值分别为4.1 K·T-1和0.2 T·K-1。当合金处于纯铁磁态和顺磁态时熵变磁熵变几乎为零,但磁场诱导的磁相变,会导致某一定温度下合金磁熵变有一个突变。但合金最大熵变并不是随磁场的增加而线性增加,当磁场达到一定值后随磁场增加其值基本没有变化。不同模型计算的制冷能力均随磁场的增加而呈线性增加。在两相共存态中,同一温度下两种不同铁磁的磁化率存在差异,即因磁场诱导的铁磁态相与合金中本身的铁磁态相的磁化率存在差异,且前者小于后者,这种物理现象对深入研究温度诱导和磁场诱导磁相变的差异有一定的参考价值。

Taking La Fe13-xSixalloys as the research object,we studied the problems of the critical magnetic field HC of the field-induced magnetic phase transition,TCof the temperature-induced magnetic phase transition,magnetic hysteresis,entropy change,and magnetic refrigeration capacity calculation,respectively. The analysis showed that the values of ΔHC/ ΔT and ΔTC/ ΔH are about 0. 2 T·K- 1and 4. 1 K·T- 1,respectively. When the alloy was in pure ferromagnetic or paramagnetic,its magnetic entropy change was almost zero,but the magnetic phase transition induced by the magnetic field,which led to a certain temperature alloy magnetic entropy change have a mutation.The alloy maximum entropy change did not add linearly with magnetic field,when the magnetic field reached a certain value increases with increasing magnetic field whose value has not changed. Along with refrigeration capacity of different models of computation and the change of the magnetic field,its value increased with increasing magnetic field increases linearly. While in the two-phase coexistence,and at same temperature the magnetization different ferromagnetic rate had difference,because of ferromagnetic and alloy magnetic field induced magnetic induction of the magnetic susceptibility and itself phase existed differences and unequal,the former than the latter,which is a new physical phenomenon and has a certain reference value.