Effect of the Magnetic Prehistory on the Low-Temperature Heat Capacity of the La(Fe0.88Al0.12-xSix)13 Compounds

Abstract

The measured heat capacity C of solids is thought in general to involve the change of the internal energy which is a state property. Therefore the electron density of states at the Fermi level is derived from the low-temperature data C=γ T + β T3. The La(Fe0.88Al 0.12-xSix)13 compounds are the antiferromagnets (AFM) TN=200 K with 0<x<0.03 and the ferromagnets (FM) with 0.03<x<0.12 TC=194 K. For x=0.024 and x=0.027 a metamagnetic phase transition from AFM to the field-induced FM (FIFM) occurs in low external magnetic field. The FIFM state of the sample remains if the magnetic field turns off. The measurements of the low-temperature heat capacity in this FIFM state have shown an increase of coefficient γ in comparison with the value both the AFM and the FM. The measured heat capacity depends on a thermodynamic path and thus is not a state property. The change of the work of the magnetostrictive strain of the sample as a part of the low-temperature heat capacity is discussed. © 2010 IOP Publishing Ltd