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YFeO and LaFeO are members of the rare-earth orthoferrites family with Pbnm space group. Using inelastic neutron scattering, the low-energy spin excitations have been measured around the magnetic Brillouin zone center. Splitting of magnon branches and finite magnon gaps (∼2 meV) are observed for both compounds, where the Dzyaloshinsky-Moriya interactions account for most of this gap with some additional contribution from single-ion anisotropy. We also make comparisons with multiferroic BiFeO (R3c space group), in which similar behavior was observed. By taking into account all relevant local Dzyaloshinsky-Moriya interactions, our analysis allows for the precise determination of all experimentally observed parameters in the spin-Hamiltonian. We find that different properties of the Pbnm and R3c space group lead to the stabilization of a spin cycloid structure in the latter case but not in the former, which explains the difference in the levels of complexity of magnon band structures for the respective compounds.

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The magnetic properties of newly prepared Tm 2 Ir 2 O 7 were investigated by means of magnetization and specific heat measurements and compared to the properties of other heavy rare-earth pyrochlore iridates. A bifurcation of zero-field-cooled and fieldcooled magnetization coinciding with the onset of the specific heat anomaly indicated the magnetic ordering of the Ir sublattice, in agreement with studies on other pyrochlore iridates. The phase diagram depicting the ordering/metal-insulator-transition temperature dependent on the rare-earth ionic radius was updated and completed. Magnetic dc susceptibilities and magnetic contributions to the specific heat of Er, Tm, and Yb analogues were well described by crystal field parameters and eigenenergies, previously reported for Er 2 Ir 2 O 7 and Yb 2 Ir 2 O 7 . The crystal field parameters for, the so-far-unstudied, Tm 2 Ir 2 O 7 were calculated by scaling the Er 2 Ir 2 O 7 parameters employing appropriate Stevens factors for Er 3+ and Tm 3+ . Iridates with the Kramers' Er 3+ and Yb 3+ ions revealed a splitting of the ground-state doublet, leading to a broad anomaly in specific heat at around 2 K and 3 K, respectively. The previously reported low value of magnetic moment in Yb 2 Ir 2 O 7 was confirmed by magnetization measurements. The nonmagnetic ground-state crystal-field singlet in Tm 2 Ir 2 O 7 dictated by Tm trigonal Wyckoff position was confirmed by both evolution of specific heat at low temperature and temperature dependence of the magnetic entropy.

CePd 2 Al 2−x Ga x compounds crystallizing in the tetragonal CaBe 2 Ge 2 -type structure (space group P 4/nmm) and undergoing a structural phase transition to an orthorhombic structure (Cmme) at low temperatures were studied by means of neutron scattering. The amplitude-modulated magnetic structure of CePd 2 Al 2 is described by an incommensurate propagation vector k = (δ x , 1 2 + δ y ,0) with δ x = 0.06 and δ y = 0.04. The magnetic moments order antiferromagnetically within the ab planes stacked along the c axis and are arranged along the direction close to the orthorhombic a axis with a maximum value of 1.5(1) μ B /Ce 3+ . CePd 2 Ga 2 reveals a magnetic structure composed of two components: the first is described by the propagation vector, 0), and the second one propagates with k 2 = (0, 1 2 ,0). The magnetic moments of both components are aligned along the same direction-the orthorhombic [100] direction-and their total amplitude varies depending on the mutual phase of magnetic moment components on each Ce site. The propagation vectors k 1 and k 2 describe also the magnetic structure of substituted CePd 2 Al 2−x Ga x compounds, except the one with x = 0.1. CePd 2 Al 1.9 Ga 0.1 with magnetic structure described by k and k 1 stays on the border between pure CePd 2 Al 2 and the rest of the series. Determined magnetic structures are compared with other Ce 112 compounds. Inelastic neutron scattering experiments disclosed three nondispersive magnetic excitations in the paramagnetic state of CePd 2 Al 2 , while only two crystal field (CF) excitations are expected from the splitting of ground state J = 5 2 of the Ce 3+ ion in a tetragonal/orthorhombic point symmetry. Three magnetic excitations at 1.4, 7.8, and 15.9 meV are observed in the tetragonal phase of CePd 2 Al 2 . A structural phase transition to an orthorhombic structure shifts the first excitation up to 3.7 meV, while the other two excitations remain at almost the same energy. The presence of an additional magnetic peak is discussed and described within the Thalmeier-Fulde CF-phonon coupling (i.e., magnetoelastic coupling) model generalized to the tetragonal point symmetry. The second parent compound CePd 2 Ga 2 does not display any sign of additional magnetic excitation. The expected two CF excitations were observed. The development of magnetic excitations in the CePd 2 Al 2−x Ga x series is discussed and crystal field parameters determined.