Magnetic properties and magnetocaloric effect in ndxla1-xfe11.5al1.5 compounds

Vol 17 No 8, August 2008
1674-1056/2008/17(08)/3087-06

Chinese Physics B

c 2008 Chin. Phys. Soc. and IOP Publishing Ltd

Magnetic properties and magnetocaloric effect in
NdxLa1−xFe11.5Al1.5 compounds∗
Wang Fang(王 芳)† , Wang Guang-Jun(王光军),
Sun Ji-Rong(孙继荣), and Shen Bao-Gen(沈保根)
State Key Laboratory of Magnetism, Institute of Physics and Centre for Condensed Matter Physics,
Chinese Academy of Sciences, Beijing 100190, China
(Received 6 November 2007; revised manuscript received 24 March 2008)
Effects of Nd-doping on the magnetic properties and magnetocaloric effects (MCEs) of Ndx La1−x Fe11.5 Al1.5 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 Nd0.2 La0.8 Fe11.5 Al1.5 characterized by the occurrence of two phase transitions at ∼188 K (PM–AFM) and ∼159 K (AFM–FM). As a result, a table-like MCE (9 J/kg·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.

Keywords: magnetic properties, NaZn13 -type compounds, magnetic entropy change
PACC: 7530S, 6540, 7550E, 0570F

NaZn13 -type LaFe-based compounds La(Fe,Si)13 and La(Fe,Al)13 have recently attracted much attention due to their potential applications in magnetic refrigeration.[1−3] La(Fe,Al)13 compounds with different Al content show diverse magnetic properties, and their properties are easily modified by magnetic field, pressure, temperature and composition.[4−11]
The ground magnetic state of La(Fe,Al)13 compounds with high Fe concentration is antiferromagnetic.