Griffiths-like behavior in Ge-rich magnetocaloric compounds Gd5(SixGe1-x)4.

The unusual low field magnetic behavior is revealed in the dc and ac magnetic susceptibility measurements of Gd5(SixGe1-x)4 (x<∼0.5). These anomalies can be ascribed to the presence of short range ferromagnetic correlations and ferromagnetic clustering in both antiferromagnetic and paramagnetic states. As a result, a novel triangular regime is discovered in the low field magnetic and crystallographic temperature-composition (T-x) phase diagram. The nature of paramagnetic state in this regime can be understood within the framework of Griffiths-like model, which not only originates from the disorder and the modification of competing interslab and intraslab magnetic exchange interactions induced by orthorhombic-monoclinic structural distortion but also correlates with the thermal history or initial magnetic disordering. [ABSTRACT FROM AUTHOR]