Tuning of the Structure and Magnetocaloric Effect of Mn(1−x)Zr(x)CoGe Alloys (Where x = 0.03, 0.05, 0.07, and 0.1)

The aim of the present work is to study the influence of a partial substitution of Mn by Zr in MnCoGe alloys. The X-ray diffraction (XRD) studies revealed a coexistence of the orthorhombic TiNiSi-type and hexagonal Ni(2)In- type phases. The Rietveld analysis showed that the changes in lattice constants and content of recognized phases depended on the Zr addition. The occurrence of structural transformation was detected. This transformation was confirmed by analysis of the temperature dependence of exponent n given in the relation ΔS(M) = C·(B(MAX))(n). A decrease of the Curie temperature with an increase of the Zr content in the alloy composition was detected. The magnetic entropy changes were 6.93, 13.42, 3.96, and 2.94 J/(kg K) for Mn(0.97)Zr(0.03)CoGe, Mn(0.95)Zr(0.05)CoGe, Mn(0.93)Zr(0.07)CoGe, and Mn(0.9)Zr(0.1)CoGe, respectively. A significant rise in the magnetic entropy change for samples doped by Zr (x = 0.05) was caused by structural transformation.