Magnetic properties and magnetocaloric effect in NdxLa1-xFe11.5Al1.5 compounds

Effects of Nd-doping on the magnetic properties and magnetocaloric effects (MCEs) of Ndmagnetic properties, NaZnmagnetic properties, NaZn$_{13}$-type compounds, magnetic entropy changeProject supported by the National Natural Science Foundation of China (Grant Nos 50571112 and 50731007), the National Basic Research Program of China (Grant No 2006CB601101) and the Basic Research Program of Chinese Academy of Science (Grant No KJCX2-YW-W02s).7530S, 6540, 7550E, 0570FEffects of Nd-doping on the magnetic properties and magnetocaloric effects (MCEs) of Nd$_{x}$La$_{1 - x}$Fe$_{11.5}$Al$_{1.5}$ have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic (AFM) coupling and an enhancement of the ferromagnetic (FM) coupling. This in turn results in a complex magnetic behaviour for Nd$_{0.2}$La$_{0.8}$Fe$_{11.5}$Al$_{1.5}$ characterized by the occurrence of two phase transitions at $\sim$188\,K (PM--AFM) and $\sim $159\,K (AFM--FM). As a result, a table-like MCE (9\,J/kg$\cdot$K) is found in a wide temperature range (160--185\,K) for a field change of 0--5\,T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM--FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.