Complex magnetic properties in the mixed 4f -5d double perovskite iridates Ln2ZnIrO6 (Ln = Nd, Sm, Eu & Gd)

TL;DR

This study synthesizes and characterizes a series of double perovskites with magnetic 4f ions and spin-orbit coupled 5d Ir, revealing diverse magnetic behaviors influenced by the rare earth element.

Contribution

It provides new insights into the magnetic properties of Ln2ZnIrO6 double perovskites with various rare earths, highlighting complex magnetic interactions involving 4f and 5d ions.

Findings

Gd2ZnIrO6 and Eu2ZnIrO6 show weak canted antiferromagnetism below 23 K and 12 K.

Sm2ZnIrO6 exhibits antiferromagnetic order at 13 K.

Nd2ZnIrO6 displays complex magnetic behavior with field-dependent phases and a neutron diffraction study of its ground state.

Abstract

In this work, we report on the synthesis and magnetic properties of a series of double perovskites Ln$_2$ZnIrO$_6$ with Ln = Nd, Sm, Eu & Gd. These compounds present new examples of the rare case of double perovskites (general formula A$_2$BB'O$_6$) with a magnetic 4f -ion on the A-site in combination with the strongly spin-orbit coupled 5d-transition metal ion Ir$^{4+}$ on the B-sublattice. We discuss the impact of different rare earths on the macroscopic magnetic properties. Gd$_2$ZnIrO$_6$ and Eu$_2$ZnIrO$_6$ show weak canted antiferromagnetic order below T$_N$ = 23 K and T$_N$ = 12 K, respectively. Sm$_2$ZnIrO$_6$ orders antiferromagnetically at T$_N$ = 13 K. Nd$_2$ZnIrO$_6$ exhibits complex magnetic properties with strong field dependence ranging from a two-step behavior at H = 0.01 T to an antiferromagnetic ground state at intermediate external fields and a spin-flop phase at H$\geq$4 T, which suggests complex interplay between Nd$^{3+}$ and Ir$^{4+}$ . To further shed light on this magnetic interaction, the magnetic structure of Nd$_2$ZnIrO$_6$'s ground state is examined via neutron powder diffraction.