Magnetic properties of rare earth and transition metal based perovskite type high entropy oxides

High entropy oxides (HEO) are a recently introduced class of oxide materials, which are characterized by a large number of elements (i.e. five or more) sharing one lattice site which crystallize in a single phase structure. One complex example of the rather young HEO family are the rare-earth transition metal perovskite high entropy oxides. In this comprehensive study, we provide an overview over the magnetic properties of three perovskite type high entropy oxides. The compounds have a rare-earth site which is occupied by five different rare-earth elements, while the transition metal site is occupied by a single transition metal. In this way a comparison to the parent binary oxides, namely the orthocobaltites, -chromites and -ferrites is possible. X-ray absorption near edge spectroscopy (XANES), magnetometry and M\"ossbauer spectroscopy are employed to characterize these complex materials. In general, we find surprising similarities to the magnetic properties of the binary oxides, despite the chemical disorder on the rare-earth site. However distinct differences and interesting magnetic properties are also observed such as noncollinearity, spin reorientation transitions as well as large coercive fields of up to 2\,T at ambient temperature. Both the chemical disorder on the RE A-site, and the nature of the TM on the B-site play an important role in the physical properties of these high entropy oxides.