Abstract
In this paper, we report on the synthesis and magnetic properties of a series of double perovskites Ln2ZnIrO6 with Ln = Nd, Sm, Eu, Gd. These compounds present examples of the rare case of double perovskites (general formula A2BB′O6) with a magnetic 4f ion on the A site in combination with the strongly spin-orbit coupled 5d transition-metal ion Ir4+ on the B sublattice. We discuss the impact of different rare earths on the macroscopic magnetic properties. Gd2ZnIrO6 and Eu2ZnIrO6 show ferrimagnetic or canted antiferromagnetic order below TN = 23 and 12 K, respectively. Sm2ZnIrO6 orders antiferromagnetically at TN = 13 K. Nd2ZnIrO6 exhibits more complex magnetic properties with a strong field dependence ranging from a two-step spin reorientation at μ0H = 0.01 T to an antiferromagnetic ground state at intermediate external fields to a spin-flop phase for 0H ≥ 4 T. This unique behavior suggests an interesting interplay between Nd3+ and Ir4+. To further shed light on the relevant magnetic interaction, the zero-field magnetic ground state of Nd2ZnIrO6 is examined via neutron powder diffraction. In general, the magnetic properties of Ln2ZnIrO6 hint towards a substantial contribution of the rare-earth ions and a significant correlation between 5d and 4f magnetism.
