Magnetic and Magnetocaloric Effect of Laves Phase Compounds Er(Fe0.8-xMn0.2-yCox+y)2 with x, y=0.0 or 0.1

Magnetic and magnetocaloric effect (MCE) of the Er(Fe0.8-xMn0.2-yCox+y)(2) Laves phase-type compounds have been investigated. X-ray diffraction (XRD) analysis has revealed that these compounds crystallize with the C15 type Laves phase structure (Space Group Fd-3m). The magnetization curves indicate a ferri-magnetic-ordering resulting of the antiparallel coupling between the moments of the heavy rare earth Er and the transition metal (TM). The partial substitution of Fe/Mn by Co increases the Curie temperature from 355 K for Er(Fe0.8Mn0.2)(2) to 475, 550, and 555 K for Er(Fe0.7Mn0.2Co0.1)(2), Er(Fe0.8Mn0.1Co0.1)(2), and Er(Fe0.7Mn0.1Co0.2)(2), respectively. According to the nature of the TM elements, arguments were presented forwards either Molecular Field or Spin Fluctuation Theory, even Stoner type pictures should be considered for. MCE was calculated according to the Maxwell relation based on isotherm magnetization measurements. The magnetic entropy change (- increment S-M) observed on a 300-400 K temperature range can be understood in terms of a Spin Fluctuation Theory picture supported by both the different magnetic polarization levels that were shared by the TM elements and the related interatomic exchange forces.