Unexpected magnetism, and transport properties in mixed lanthanide compound.*

For intelligent materials design it is desirable to have compounds which have multiple functionalities such as a large magnetoresistance, ferromagnetic and ferrimagnetic states, and field-induced first-order metamagnetic transitions. Here, we discuss one such example where we have combined two lanthanide elements Pr and Er in Pr$_{\mathrm{0.6}}$Er$_{\mathrm{0.4}}$Al$_{\mathrm{2}}$. This compound exhibits multiple functionalities in magnetic fields between 1 and 40 kOe. It undergoes only a trivial ferrimagnetism to paramagnetism transition in a zero magnetic field, but Pr$_{\mathrm{0.6}}$Er$_{\mathrm{0.4}}$Al$_{\mathrm{2}}$ exhibits a large positive magnetoresistance (MR) for H$\ge $40 kOe, a small but non negligible negative MR for H$\le $30 kOe, and a clear Griffiths-like phase behavior at \textless 1 kOe. The compound also exhibits an asymmetry of hysteresis loop, or exchange bias (EB) effect after field cooling from the paramagnetic state. These phenomena are attributed to the competition between single-ion anisotropies of Pr and Er ions coupled with the opposite nearest-neighbor and next-nearest-neighbor exchange interactions.