The first rare earth based high entropy alloy (HEA) with almost equimolar composition of elements Ho, Dy, Y, Gd, and Tb has been synthesized three years ago [M. Feuerbacher et al, Mater. Res. Lett. 3, 1-6 (2015)]. The alloy obtains a hexagonal, single phase crystal structure. As the mutual mixing enthalpies of the elements are zero, the Ho-Dy-Y-Gd-Tb HEA may be considered as a prototype of an ideal HEA.

We have studied magnetic properties, temperature dependent specific heat and electrical resistivity, and magnetoresistivity of the Ho–Dy–Y–Gd–Tb HEA and three additional members of the rare earth based HAEs: Ho-Tb-Dy-Gd-Lu, Ho-Tb-Dy-Er-Tm, and Ce-Gd-Tb-Dy-Ho.

A typical magnetic phase diagram constructed from experimentally determined physical properties will be presented. The magnetic phase diagram demonstrates four regions: paramagnetic phase above the Néel temperature of approximately 180 K, hexagonal antiferromagnetic phase, field induced ferromagnetic phase and a spin glass phase below 10 K.