The field of double perovskites is now advancing to three magnetic elements on the A, B and B′ sites. A series of iridium-based double perovskite compounds, Ln2CoIrO6 (Ln=Eu, Tb, Ho), with three magnetic elements was synthesized as polycrystalline samples. The compounds crystalize in monoclinic structures with the space group P21/n. Magnetic properties of these hetero-tri-spin 3d-5d-4f systems were studied by magnetic susceptibility and field dependent magnetization in both DC and pulsed magnetic fields. All these compounds show ferrimagnetic transitions at temperatures TC above 100 K, which are attributable to antiferromagnetic coupling between Co2+ and Ir4+ spins. For Eu2CoIrO6, the magnetic properties are similar to those of La2CoIrO6. The Eu3+ spins show Van Vleck paramagnetism, and do not significantly interact with transition-metal cations. In contrast, Tb2CoIrO6 and Ho2CoIrO6 reveal a second transition to antiferromagnetic order below a lower temperature TN. The temperature-induced ferrimagnetic-to-antiferromagnetic phase transition might be explained by a spin-reorientation transition. Moreover, a magnetic-field-induced spin-flop-like transition with a small hysteresis was observed below TN in these two compounds. The magnetic moments of all three compounds do not saturate up to 60 T at low temperatures. A moderate magnetocaloric effect was also observed in all three compounds. Our results should motivate further investigation of the spin configuration on single crystals of these iridium-based double perovskites.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics