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The CeTX3 compounds belong to the intensively studied group of materials revealing such properties as valence fluctuations, heavy-fermion behavior, or pressure-induced superconductivity. So far, magnetic structure was investigated in only a few of these. We performed a series of neutron-diffraction experiments on a structurally well-defined CeCuAl3 single crystal. The ordered non-centro-symmetric tetragonal BaNiSn3-type (I4mm) crystal structure as well as the antiferromagnetic order below TN≈2.7 K were corroborated by our diffraction experiments. The amplitude modulated magnetic structure with in-plane magnetic moments described by the propagation vector k=(0.4,0.6,0) was revealed. The relation between structural parameters and magnetic structures in the family of isostructural CeTX3 compounds is discussed. [ABSTRACT FROM AUTHOR]

The magnetization and electrical resistivity measurements on a CePdIn single crystal as well as its preparation and structural characterization are presented. The negative paramagnetic Curie temperatures indicate antiferromagnetic ground state, the anisotropy of the paramagnetic Curie temperature amounts 22.7 K. No ferromagnetic correlations were indicated. Powder neutron diffraction experiment performed at temperatures down to 0.4 K did not lead to observation of any magnetic peak in diffraction patterns. We estimate the magnetic moment on Ce atoms to be significantly lower than 0.5 μB. The temperature development of lattice parameters documents the standard thermal expansion of the unit cell; no signs of structural phase transition were observed. [ABSTRACT FROM AUTHOR]

We report on the magnetic structures in the TbNiAl1-xInx compounds as determined by powder neutron diffraction. These compounds belong to a large family of ternary rare-earth intermetallics crystallizing in the ZrNiAl-type hexagonal structure. All studied compounds order magnetically with magnetic structures characterized by k1 = (0,0,0) and k2 = (1/2,0, 1/2) propagation vectors and magnetic moments aligned along or perpendicular to the hexagonal c axis. The magnetocrystalline anisotropy changes from uniaxial in the In-poor compounds (x ≤ 0.4) to planar in the In-rich compounds (x ≥ 0.5). The change of magnetocrystalline anisotropy type is a consequence of the development of structural parameters in the studied series. The Tb moments are oriented along the c axis when the nearest Tb-Tb distances between the planes are large compared to those within the planes, whereas Tb moments lie within the basal planes in the opposite case. This picture relating the structural parameters and anisotropy type can be generalized to the whole group of Tb-based compounds with the ZrNiAl type of structure. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of magnetism in the DyNi1−x Cu x Al pseudoternary series was studied. The results of magnetization, magnetic susceptibility, heat capacity and neutron diffraction experiments are summarized and discussed in context of other RNi1−x Cu x Al pseudoternaries. The compounds with x ≤ 0.2 adopt the coexistence of antiferromagnetic and ferromagnetic order similar to that one in the parent DyNiAl. The compounds with 0.3 ≤x ≤ 0.6 exhibit antiferromagnetic order only while the compounds with x ≥ 0.9 are ferromagnets. The compounds with 0.6 ≤x ≤ 0.9 exhibit signs of short-range correlations, especially the compound with x = 0.8 does not show any long-range magnetic order at all. It is in accordance with previously studied series. [Copyright &y& Elsevier]

The ErNi1-xCuxAl compounds have been studied from the view of crystallographic structure and magnetic properties by means of X-ray and neutron diffraction, magnetization and heat capacity measurements. The hexagonal ZrNiAl-type crystal structure adopted by the parent compounds ErNiAl and ErCuAl is conserved over the entire composition range. The concentration dependence of lattice parameters shows a discontinuity between x=0.5 and 0.6 both in paramagnetic and magnetically ordered phase. The evolution of magnetism from antiferromagnetism (AF) with Er-moments within the basal plane in ErNiAl to the simple ferromagnetism (F) with moments along the c-axis in ErCuAl is rather complex. The AF ordering is characterized by a propagation vector (1/2,0,1/2) with moments within the basal plane in the low Cu-concentration region for x up to 0.40. An incommensurate component with Er-moments along c develops within the range of 0.20⩽x⩽0.40 and grows on account of the commensurate one. The ErNi0.5Cu0.5Al is a simple F with moments along c. For concentrations with x=0.6 and 0.8 signs of short-range ordering were revealed. [Copyright &y& Elsevier]

We present a neutron powder diffraction study on TmCuAl, crystallizing in the ZrNiAl-type hexagonal structure. Our data confirm magnetic ordering below Tc=1.9 K. The magnetic structure is a longitudinal spin wave described by a propagation vector k=(1/20q) with Tm magnetic moments along the c-axis. In addition to that, a commensurate antiferromagnetic component within the basal plane with k=(1/201/2 0 q) with Tm magnetic moments along the c-axis. In addition to that, a commensurate antiferromagnetic component within the basal plane with k=(1/201/2 0 1/2) develops below the magnetic phase transition at T1≅1.2 K. It leads to a rather complex magnetic structure below T1. One-third of the thulium moments has a considerably reduced magnitude compared to the remaining ones. No further phase transitions were observed down to 50 mK. [Copyright &y& Elsevier]

Structural, magnetic and electrical transport properties of a new compound, NpIrSn, crystallizing in the ZrNiAl-type hexagonal structure are reported. NpIrSn orders antiferromagnetically below TN=40 K and undergoes a second magnetic phase transition around 22 K. The antiferromagnetic order is not affected by magnetic fields up to 9 T. Powder neutron diffraction revealed an incommensurate magnetic structure in both magnetic phases. [Copyright &y& Elsevier]

Abstract: Results of crystal and magnetic structure study of DyNi1−x Cu x Al quasiternary compounds are presented and discussed in context with results of previous investigations of analogous compounds with Tb and Er. This allows to draw conclusions with more general validity for this type of materials with heavy rare earths showing common anomalies of lattice parameters (a and c) and evolution of magnetism with respect to the composition of the Ni,Cu sublattice. The opposite steps in the a(x) and c(x) dependences compensate and have no effect on the lattice volume. On the other hand, these anomalies yield discontinuity of the c/a concentration dependence and manifest existence of a “forbidden”c/a ratio around c/a (≈0.56–0.57) in RTX compounds with the hexagonal ZrNiAl structure. The loss of magnetic long-range order, which is generally observed around x =0.8, is not coupled with the structure anomaly but the number of 3d electrons in the Ni, Cu sublattice seems to be the crucial parameter. [Copyright &y& Elsevier]

UNiAl, which orders below TN=19.3 K antiferromagnetically (AF), exhibits pronounced magnetic-history-dependent phenomena. This concerns all bulk magnetic properties and also the microscopic magnetic structures. When a magnetic field larger than 7–8 T is applied along the c-axis at temperatures below 7 K, the zero-field-cooled AF structure characterized by a propagation vector (0.1, 0.1, 0.5), is transformed into a new AF structure with a propagation vector (0.173, 0, 0.5) that persists down to zero field. Uranium moments are in both structures sine-wave modulated with a similar magnitude of 1.2–1.3μB/U, however, the modulation is in different directions. Effective Ni-mediated interactions along distinct chains of ions are likely responsible for the change in the basal-plane component of the propagation vector. [Copyright &y& Elsevier]

We have investigated the effect of hydrostatic pressure on magnetic properties of TbNiAl, crystallizing in hexagonal ZrNiAl-type structure. TbNiAl orders antiferromagnetically below TN = 45 K and undergoes further magnetic phase transition to another AF phase at T1 = 23 K. The magnetic field of Bc ≅= 0:3 T applied along the c-axis at 2 K leads to the transition to ferromagnetic order. By applying the hydrostatic pressure, both TN and T1 remain almost unaffected whereas Bc shows a strong increase. The hydrostatic pressure stabilizes the antiferromagnetic state which can be related to development of structural parameters. [ABSTRACT FROM AUTHOR]