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Register a new userA comparative study on magnetic order and field induced magnetic transition on two series of double perovskite iridates RE2BIrO6 (RE=Pr,Nd,Sm,Eu,Gd B=Zn,Mg)
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We perform a comparative magnetic study on two series of rare-earth (RE) based double perovskite iridates RE2BIrO6 (RE=Pr,Nd,Sm-Gd;B=Zn,Mg), which show Mott insulating state with tunable charge energy gap from ~330 meV to ~560 meV by changing RE cations. For nonmagnetic RE=Eu cations, Eu2MgIrO6 shows antiferromagnetic (AFM) order and field-induced spin-flop transitions below Neel temperature (TN) in comparison with the ferromagnetic (FM)-like behaviors of Eu2ZnIrO6 at low temperatures. For magnetic-moment-containing RE ions, Gd2BIrO6 show contrasting magnetic behaviors with FM-like transition (B=Zn) and AFM order (B=Mg), respectively. While, for RE=Pr, Nd and Sm ions, all members show AFM ground state and field-induced spin-flop transitions below TN irrespective of B=Zn or Mg cations. Moreover, two successive field-induced metamagnetic transitions are observed for RE2ZnIrO6 (RE=Pr,Nd) in high field up to 56 T, the resultant field temperature (H-T) phase diagrams are constructed. The diverse magnetic behaviors in RE2BIrO6 reveal that the 4f-Ir exchange interactions between the RE and Ir sublattices can mediate their magnetism.
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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$_2$BBO$_6$) 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.
We have studied the thermal conductivity $kappa$ on single crystalline samples of the antiferromagnetic monolayer cuprates R$_2$CuO$_4$ with R = La, Pr, Nd, Sm, Eu, and Gd. For a heat current within the CuO$_2$ planes, i.e. for $kappa_{ab}$ we find high-temperature anomalies around 250 K in all samples. In contrast, the thermal conductivity $kappa_c$ perpendicular to the CuO$_2$ planes, which we measured for R = La, Pr, and Gd, shows a conventional temperature dependence as expected for a purely phononic thermal conductivity. This qualitative anisotropy of $kappa_i$ and the anomalous temperature dependence of $kappa_{ab}$ give evidence for a significant magnetic contribution $kappa_{mag}$ to the heat transport within the CuO$_2$ planes. Our results suggest, that a large magnetic contribution to the heat current is a common feature of single-layer cuprates. We find that $kappa_{mag}$ is hardly affected by structural instabilities, whereas already weak charge carrier doping causes a strong suppression of $kappa_{mag}$.
New frustrated antiferromagnetic compounds CuRE2Ge2O8 (RE=Pr, Nd, Sm, Eu) have been investigated using high-resolution x-ray diffraction, magnetic and heat capacity measurements. These systems show different magnetic lattices depending on rare-earth element. The nonmagnetic Eu compound is a S=1/2 two-dimensional triangular antiferromagnetic lattice oriented in the ac plane with geometrical frustration. On the other hand, the Pr, Nd, and Sm compounds show a three-dimensional honeycomb-tunnel-like lattice made of RE^3+ running along the a axis with the characteristic behavior of frustrated antiferromagnets.
We present a systematic study of the structural and magnetic properties of two branches of the rare earth Tripod Kagome Lattice (TKL) family A$_{2}$RE$_{3}$Sb$_{3}$O$_{14}$ (A = Mg, Zn; RE = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation textit{A-RE}, as in textit{MgPr} for Mg$_{2}$Pr$_{3}$Sb$_{3}$O$_{14}$), which complements our previously reported work on textit{MgDy}, textit{MgGd}, and textit{MgEr} cite{TKL}. The present susceptibility ($chi_{dc}$, $chi_{ac}$) and specific heat measurements reveal various magnetic ground states, including the non-magnetic singlet state for textit{MgPr}, textit{ZnPr}; long range orderings (LROs) for textit{MgGd}, textit{ZnGd}, textit{MgNd}, textit{ZnNd}, and textit{MgYb}; a long range magnetic charge ordered state for textit{MgDy}, textit{ZnDy}, and potentially for textit{MgHo}; possible spin glass states for textit{ZnEr}, textit{ZnHo}; the absence of spin ordering down to 80 mK for textit{MgEr}, textit{MgTb}, textit{ZnTb}, and textit{ZnYb} compounds. The ground states observed here bear both similarities as well as striking differences from the states found in the parent pyrochlore systems. In particular, while the TKLs display a greater tendency towards LRO, the lack of LRO in textit{MgHo}, textit{MgTb} and textit{ZnTb} can be viewed from the standpoint of a balance among spin-spin interactions, anisotropies and non-Kramers nature of single ion state. While substituting Zn for Mg changes the chemical pressure, and subtly modifies the interaction energies for compounds with larger RE ions, this substitution introduces structural disorder and modifies the ground states for compounds with smaller RE ions (Ho, Er, Yb).
We report a comprehensive investigation of Ln2NiIrO6 (Ln = La, Pr, Nd) using thermodynamic and transport properties, neutron powder diffraction, resonant inelastic x-ray scattering, and density functional theory (DFT) calculations to investigate the role of A-site cations on the magnetic interactions in this family of hybrid 3d-5d-4f compositions. Magnetic structure determination using neutron diffraction reveals antiferromagnetism for La2NiIrO6, a collinear ferrimagnetic Ni/Ir state that is driven to long range antiferromagnetism upon the onset of Nd ordering in Nd2NiIrO6, and a non-collinear ferrimagnetic Ni/Ir sublattice interpenetrated by a ferromagnetic Pr lattice for Pr2NiIrO6. For Pr2NiIrO6 heat capacity results reveal the presence of two independent magnetic sublattices and transport resistivity indicates insulating behavior and a conduction pathway that is thermally mediated. First principles DFT calculation elucidates the existence of the two independent magnetic sublattices within Pr2NiIrO6 and offers insight into the behavior in La2NiIrO6 and Nd2NiIrO6. Resonant inelastic x-ray scattering is consistent with spin-orbit coupling splitting the t2g manifold of octahedral Ir4+ into a Jeff = 1/2 and Jeff = 3/2 state for all members of the series considered.
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