La0.6Pr0.5Fe11.5-xCoxSi1.5合金的磁性和磁热效应

Magnetic Properties and Magnetocaloric Effect of La_(0.6)Pr_(0.5)Fe_(11.5-x)Co_xSi_(1.5)

使用电弧炉熔炼法制备了La0.6Pr0.5Fe11.5-xCoxSi1.5(x=0,0.1,0.2,0.3,0.4,0.5和0.6)系列合金。XRD分析与SEM成分分析表明该系列合金中除含有少量富镧相(P4/nmm)和α-Fe相外,均由NaZn13型立方结构单相组成,晶格常数随着Co含量的增加基本保持不变。磁性测量表明该系列合金的TC随着Co含量的增加呈线性增加,当x=0.6时,TC达264K。合金的升、降温磁化曲线随着Co含量的增加逐渐重合,即表明该系列合金的热滞随着Co含量的增加而减小;利用Maxwell方程计算得出在x=0时,合金在ΔB=1.5T的外磁场下-ΔSm达到38.4J.kg-.1K-1。这种磁熵变来源于外磁场引起的一级相变,随着Co含量的增加-ΔSm线性减小,这是由于Co含量的增加使合金的磁相变出现由一级相变向二级相变转变。

The La0.6Pr0.5Fe11.5-xCoxSi1.5 （x = 0, 0.1, 0.2, 0.3, 0.4, 0. 5 and 0.6） alloys were prepared by arc melting. The XRD analysis and SEM component analysis showed that the Lao.6 Pr0.5 Fe11.5-x CoxSi1.5（x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and0.6） alloys consisted of the NaZn13 cubic phase, minor amount of La rich phase （P4/nmn） and α-Fe phase, it was found that lattice parameter had few change with increasing Co content. Magnetic measurement indicated that the Curie temperature of the alloys linearly increased with increasing Co content, for x = 0.6, Curie temperature could reach 264 K. The thermal hysteresis of alloys decreased with magnetic entropy changes increasing Co content. The -ΔSm were calculated from the isothermal magnetizations by using the maxwell relation, for x = 0, magnetic entropy changes - ΔSm of alloys could up to 38.4 J.kg^-1K^-1 for a field change of 1.5 T, which was attributed to the first-order magnetic transition. The magnetic entropy changes - ΔSm of alloys linearly decreased with increasing Co content, the magnetic transition was changed from the first order magnetic transition to the second order magnetic transition with increasing Co content.