Canted Ferromagnetic Structure Research Articles

Orthogonal antiferromagnetism to canted ferromagnetism in CaCo3Ti4O12 quadruple perovskite driven by underlying kagome lattices

AA′3B4O12 quadruple perovskites, with magnetic A′ and non-magnetic B cations, are characterized by a wide range of complex magnetic structures. These are due to a variety of competing spin-exchange interactions up to the fourth nearest neighbours. Here, we synthesize and characterize the magnetic behaviour of the CaCo3Ti4O12 quadruple perovskite. We find that in the absence of an external magnetic field, the system undergoes antiferromagnetic ordering at 9.3 K. This magnetic structure consists of three interpenetrating mutually orthogonal magnetic sublattices. Under an applied magnetic field, this antiferromagnetic structure evolves into a canted ferromagnetic structure. In explaining these magnetic structures, as well as the seemingly unrelated magnetic structures found in other quadruple perovskites, we suggest a crucial role played by the underlying kagome lattices in these systems. All observed magnetic structures of these materials represent indeed one of the three possible ways to reduce spin frustration in the A′ site kagome layers. More specifically, our survey of the magnetic structures observed for quadruple perovskites AA′3B4O12 reveals the following three ways to reduce spin frustration, namely to make each layer ferromagnetic, to adopt a compromise 120° spin arrangement in each layer, or to have a magnetic structure with a vanishing sum of all second nearest-neighbour spin exchanges.

Magnetic phase diagram of the solid solution LaMn2(Ge1−xSix)2 (0 ≤ x ≤ 1) unraveled by powder neutron diffraction

The structural and magnetic properties of the ThCr2Si2-type solid solution LaMn2(Ge1−xSix)2 (x = 0.0 to 1.0) have been investigated employing a combination of X-ray diffraction, magnetization and neutron diffraction measurements, which allowed establishing a magnetic composition-temperature phase diagram. Substitution of Ge by Si leads to a compression of the unit cell, which affects the magnetic exchange interactions. In particular, the magnetic structure of LaMn2(Ge1−xSix)2 is strongly affected by the unit cell parameter c, which is related to the distance between adjacent Mn layers. Commensurate antiferromagnetic layers and a canted ferromagnetic structure dominate the Si-rich part of the solid solution, whilst an incommensurate antiferromagnetic flat spiral and a conical magnetic structure are observed in the Si-poor part.

Multi- k spin ordering in CaFe3Ti4O12 stabilized by spin-orbit coupling and further-neighbor exchange

Orthogonal spin ordering is rarely observed in magnetic oxides because nearest-neighbor symmetric Heisenberg superexchange interactions usually dominate. We have discovered that in the quadruple perovskite $\mathrm{Ca}{\mathrm{Fe}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$, where only the $S=2$ ${\mathrm{Fe}}^{2+}$ ion is magnetic, long-range magnetic order consisting of an unusual arrangement of three interpenetrating orthogonal sublattices is stabilized. Each magnetic sublattice corresponds to a set of $\mathrm{Fe}{\mathrm{O}}_{4}$ square planes sharing a common orientation. This multi-$k$ magnetic spin ordering is the result of fourth-neighbor spin couplings with a strong easy-axis anisotropy. In an applied magnetic field, each sublattice tends towards ferromagnetic alignment, but remains polarized by internal magnetic fields generated by the others, thus stabilizing in a noncollinear canted ferromagnetic structure. $\mathrm{Ca}{\mathrm{Fe}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$ provides a rare example of how nontrivial long-range spin order can arise when near-neighbor Heisenberg superexchange is quenched.

Effect of Tb substitution in naturally layered LaMn2Si2: magnetic, magnetocaloric, magnetoresistance and neutron diffraction study

Evolution of physical and magnetic properties of La rich La1−xTbxMn2Si2 (x = 0, 0.1 and 0.225) compounds is studied using temperature and field dependent dc magnetization, electrical transport, and heat capacity measurements. LaMn2Si2 undergoes a paramagnetic to antiferromagnetic ordering at TN ~ 400 K and a long range ferromagnetic ordering below TC ~ 308 K. However, the substitution of Tb at La site results in the contraction of unit cell as well as decrease in the Mn–Mn spacing, which leads to an additional antiferromagnetic phase below TN ~ 87 K and 257 K for La0.9Tb0.1Mn2Si2 and La0.775Tb0.225Mn2Si2, respectively. Using magnetization isotherm results, we have constructed an H–T phase diagram for x = 0.225 and have found the coexistence of this additional antiferromagnetic phase with ferromagnetic phase. The phase coexistence at x ~ 0.225 is further analysed using magnetoresistance (MR) and magnetocaloric effect (MCE) studies and a reasonable correlation is established between MCE and MR. In order to analyse the nature of the magnetic transition at TC, a universal master curve is constructed by rescaling the magnetic entropy curves. Low temperature neutron diffraction measurements performed on the polycrystalline samples revealed a canted ferromagnetic structure for x ~ 0.1 and a canted antiferromagnetic structure for x ~ 0.225.

Magnetic structure of La1-xTbxMn2Si2 compounds

The magnetic structure of La1-xTbxMn2Si2 compounds with 0 ≤ x ≤ 1 has been studied by powder neutron diffraction and magnetization measurements on single-crystal samples. We demonstrate that at 4.2 K, with increasing the Tb concentration, a canted ferromagnetic structure of LaMn2Si2 changes at x > 0.2 to a canted antiferromagnetic structure. The antiferromagnetic in-plane component of Mn moment decreases with increasing concentration x and vanishes at x > 0.5. TbMn2Si2 is characterized by a collinear in-plane Mn ordering and ferrimagnetic structure, in which the Mn sublattice possesses the ferromagnetic interlayer alignment along the easy c-axis. Neutron diffraction study does not reveal a long-range magnetic order of Tb moments for the compounds with x ≤ 0.4. Our results show that for concentrations 0.2 < x ≤ 0.4, a competition of the interlayer Tb-Mn, Mn-Mn exchange interactions and strong uniaxial magnetic anisotropy leads to formation of a frustrated magnetic state of Tb ions, which prevents magnetic ordering in the Tb sublattice.

Magnetic transitions and the magnetocaloric effect in the Pr1−xYxMn2Ge2 system

Layered rare earth compounds in the RMn2X2 series (R = rare‐earth; X = Ge, Si) are of interest for potential cooling applications at lower temperatures as they enable the structural and magnetic behavior to be controlled via substitution of R, Mn, and X atoms on the 2a, 4d, and 4e sites respectively. We continue investigations of the Pr1−xYxMn2Ge2 magnetic phase diagram as functions of both composition and Mn–Mn spacing using X‐ray and neutron diffraction, magnetization and differential scanning calorimetry measurements. Pr1−xYxMn2Ge2 exhibits an extended region of re‐entrant ferromagnetism around x ∼ 0.5 with re‐entrant ferromagnetism at for Pr0.5Y0.5Mn2Ge2. The entropy values −ΔSM around the ferromagnetic transition temperatures from the layered antiferromagnetic AFl structure to the canted ferromagnetic structure Fmc (typically ) have been derived for Pr1−xYxMn2Ge2 with x = 0.0, 0.2, and 0.5 for ΔB = 0–5 T. The changes in magnetic states due to Y substitution for Pr are discussed in terms of chemical pressure, external pressure, and electronic effects.

Synthesis and surface modified hard magnetic properties in Co0.5Pt0.5 nanocrystallites from a rheological liquid precursor

Small crystallites of a metastable phase Co0.5Pt0.5 are precipitated by heating a rheological liquid precursor of cobalt–hydrazine complex and platinum chloride H2PtCl6·xH2O in polymer molecules of poly(vinylpyrrolidone) (PVP) in ethylene glycol. The hydrazine co-reduces nascent atoms from the Co2+ and Pt4+ that recombine and grow as Co0.5Pt0.5. The PVP molecules cap a growing Co0.5Pt0.5 as it achieves a critical size so that it stops growing further in given conditions. X-ray diffraction pattern of a recovered powder reveals a crystalline Co0.5Pt0.5 phase (average crystallite size D∼8nm) of a well-known Fm3m-fcc crystal structure with the lattice parameter a=0.3916nm (density ρ=14.09g/cm3). A more ordered L10 phase (ρ=15.91g/cm3) transforms (D≥25nm) upon annealing the powder at temperature lesser than 700°C (in vacuum). At room temperature, the virgin crystallites bear only a small saturation magnetization Ms=5.54emu/g (D=8nm) of a soft magnet and it hardly grows on bigger sizes (D≤31nm) in a canted ferromagnetic structure. A rectangular hysteresis loop is markedly expanded on an optimally annealed L10 phase at 800°C for 60min, showing a surface modified coercivity Hc=7.781kOe with remnant ratio Mr/Ms=0.5564, and Ms=39.75emu/g. Crystallites self-assembled in an acicular shape tailor large Hc from ideal single domains and high magnetocrystalline anisotropy of a hard magnet L10 phase.

Resonant X-Ray Diffraction Study of Multipole Ordering in the Ferromagnetic Compound CePd3S4

Resonant X-ray diffraction experiments on CePd 3 S 4 were performed at the Ce- L 3 absorption edge to study the states of quadrupolar ordering below the ferromagnetic transition temperature T C = 6.3 K. The magnetic structure of CePd 3 S 4 was reported as a canted ferromagnetic structure with a canting angle of 51°. It has therefore been pointed out that the complex magnetic structure arises from the simultaneous ordering of quadrupole moments. We observed the azimuthal angle dependence of the diffraction intensity of two forbidden reflections, specifically, 003 and 104 reflections, for both π–π' and π–σ' scattering processes. The results revealed that O 2 0 -type antiferroquadrupolar ordering coexists with magnetic ordering. We infer that the magnetic structure of CePd 3 S 4 is not a canted structure but a ferrimagnetic structure and that the quadrupole moment is also a primary-order parameter. These findings well explain the anomalously high transition temperature of CePd 3 S 4 , which is very much high...

Magnetic structure of the ferromagnetic new ternary silicide Nd5CoSi2

Nd5CoSi2 was obtained from the elements by arc-melting followed by annealing at 883 K. Its investigation by single-crystal x-ray and neutron powder diffraction shows that this ternary silicide crystallizes as Nd5Si3 in a tetragonal structure deriving from the Cr5B3-type (I4/mcm space group; a = 7.7472(2) and c = 13.5981(5) Å as unit cell parameters). The structural refinements confirm the mixed occupancy on the 8h site between Si and Co atoms, as already observed for Gd5CoSi2. Magnetization and specific heat measurements reveal a ferromagnetic behavior below TC = 55 K for Nd5CoSi2. This magnetic ordering is further evidenced by neutron powder diffraction investigation revealing between 1.8 K and TC a canted ferromagnetic structure in the direction of the c-axis described by a propagation vector k = (0 0 0). At 1.8 K, the two Nd3+ ions carry ordered magnetic moments equal respectively to 1.67(7) and 2.37(7) μB for Nd1 and Nd2; these two moments exhibit a canting angle of θ = 4.3(6)°. This magnetic structure presents some similarities with that reported for Nd5Si3.

Investigation of the nature of the unusual magnetic behavior of La0.65Nd0.35Mn2Si2 compound by neutron diffraction study

The magnetic structures of the La0.65Nd0.35Mn2Si2 have been investigated by powder neutron diffraction between 5 and 350K. According to magnetic measurements this compound shows multiple magnetic phase transitions. Neutron diffraction indicates a canted ferromagnetic structure above 220 and below 46K. Between 50≤T≤70K there is a mixed phase where canted ferromagnetic and antiferromagnetic structure coexist. Moreover, La0.65Nd0.35Mn2Si2 has a two-step magnetic transition from an antiferromagnetic to ferromagnetic state between 65 and 22K. This two-step transition had not been observed so far and in this study it is studied in depth.

Magnetic Properties of New Filled Skutterudite Compounds EuT4As12(T=Fe, Ru, and Os) Synthesized under High Pressure

New As-based filled skutterudite compounds Eu T 4 As 12 ( T =Fe, Ru, and Os) have been synthesized under high pressure; these compounds have lattice constants of 8.3374, 8.5120, and 8.5504 A, respectively, which are larger than those expected from the lanthanide contraction in trivalent ions. The large lattice constants and effective magnetic moments (6.9–8.3 µ B /Eu) of the compounds suggest that Eu ions in the compounds are in a divalent or mixed-valent state. Magnetic measurements reveal that EuFe 4 As 12 and EuOs 4 As 12 exhibit ferromagnetic-like phase transitions at 152 and 25 K, respectively. By contrast, EuRu 4 As 12 shows no anomaly down to 2 K. The reciprocal susceptibility χ -1 of EuFe 4 As 12 has a nonlinear temperature dependence, which implies that the compound has a canted ferromagnetic or ferrimagnetic structure below 152 K. Furthermore, magnetization measurements of EuFe 4 As 12 show that its magnetic moment is about 4.5 µ B /Eu at 2 K, which is much less than the magnetic moment (7 µ B /...

Multi-magnetic phases in the ferromagnetic ternary silicides Nd6Co1.67Si3 and Tb6Co1.67Si3

Neutron powder diffraction experiments have been carried out on the hexagonal ternary silicides Nd6Co1.67Si3 and Tb6Co1.67Si3 in order to determine their magnetic structures. These compounds exhibit two successive ferromagnetic transitions at TC = 84 K and T1 = 40 K for Nd6Co1.67Si3 and at TC = 186 K and T1 = 171 K for Tb6Co1.67Si3. Single-crystal x-ray diffraction and specific heat measurements have been realized on Tb6Co1.67Si3 in order to complete its characterization. Neutron diffraction investigation at 1.5 K reveals for both compounds a canted ferromagnetic structure with a propagation vector k = (0 0 0). The Nd moment values are, respectively, equal to μ1 = 2.06(10)μB and μ2 = 3.14(9)μB for Nd1 and Nd2 atoms whereas Tb1 and Tb2 atoms carry a magnetic moment of μ1 = 7.9(2)μB and μ2 = 8.9(2)μB in Tb6Co1.67Si3. Moreover, a transition from a canted ferromagnet to a pure ferromagnet occurs at T1 = 40 K in Nd6Co1.67Si3 while a spin reorientation of the non-collinear ferromagnetic structure occurs at T1 = 171 K for Tb6Co1.67Si3. These magnetic structures are discussed on the basis of the atomic disorder existing for Co atoms in these ternary silicides around the Nd1 and Tb1 atoms.

Electronic structure and Fermi surface of strongly ferromagneticU2N2Z-type(Z=Sb,Te,Bi)compounds from first principles

The electronic structures of the uranium ternaries of the ${\text{U}}_{2}{\text{N}}_{2}Z$-type $(Z=\text{Sb},\text{Te},\text{Bi})$, crystallizing in the tetragonal $I4/mmm$ structure and having among uranium systems relatively high values of both their ferromagnetic (FM) transition temperatures and ordered magnetic moments (mms), have been investigated ab initio. They were calculated employing the local-spin density-functional theory with different versions of the orbital polarization correction (OPC) applied within the fully relativistic and full potential local-orbital band-structure code. The obtained results predict all these materials to be metallic both in the ferromagnetically ordered and nonmagnetically ordered (NMO) states. However, the bottoms of their conduction bands in the NMO states occur merely about 0.3 eV below the Fermi level, ${\text{E}}_{\text{F}}$, and a pronounced gap in ${\text{U}}_{2}{\text{N}}_{2}\text{Te}$ or pseudogaps in the two remaining compounds are opening just below these bands, which makes such a metallic state unstable. The considerable reduction in these gap or pseudogaps in the FM states cause a stabilization of a metallic behavior. A covalently metallic bonding character of these ternaries has been obtained in all calculations. It appeared that the only uranium atoms create predominantly metallic bonding due to a fairly strong hybridization between the U $5f$ and U $6d$ electrons. The U $5f$ electrons contributing also to the covalent bonding have somewhat dual character, i.e., partly localized and itinerant. Contrary to the Sb- and Bi-based ternaries ordered along the $c$ axis, as deduced from previous neutron powder diffraction studies, ${\text{U}}_{2}{\text{N}}_{2}\text{Te}$ has a canted FM structure with its mms tilted from the $c$ axis by about $70\ifmmode^\circ\else\textdegree\fi{}$. This fact has also been revealed by the present theoretical results. These data also point to the fact that the telluride, unlike the two other compounds, exhibits an almost half-metallic behavior. For all three ternaries, using the OPXC version of OPC the computed mms are in accord with the published experimental data. In turn, the Fermi surfaces of investigated ternaries have quasi-two-dimensional properties and quite unique nesting features along directions of their easy magnetization axes.

Influence of pressure on the stability of the magnetically ordered states in alloys of the system Mn2−xFexAs0.5P0.5

The phase diagram of the system Mn2−xFexAs0.5P0.5 under pressure is investigated experimentally and theoretically. It is found that the spontaneous and magnetic-field-induced low-temperature phase in the region 0.5⩽x&amp;lt;0.8 does not suffer significant changes under hydrostatic pressure up to 2kbar. Based on ab initio calculations of the electronic structure of the alloys Mn1.5Fe0.5As0.5P0.5, it is established that the degree of filling of the 3d electron band changes upon ferromagnetic polarization and compression of the crystal lattice. A model is proposed by which one can take into account the main features of the antiferromagnetic and canted ferromagnetic structures. The parameters of the model are the degree of filling of the d band, the nonmagnetic electronic density of states, and the intra-atomic exchange integral. Their values are estimated directly from the data of the first-principles electronic structure calculations. It is shown in the framework of the model that the stability of the magnetic characteristics of the canted ferromagnetic structure with respect to pressure is due to an increase of the number of electrons in the magnetically active band upon a decrease of the unit cell volume.

Peculiarities of the spontaneous and magnetic-field-induced magnetically ordered phases in alloys of the Mn2−xFexAs0.5P0.5 system

The phase diagram of the system Mn2−xFexAs0.5P0.5 is investigated experimentally and theoretically. The existence of an antiferromagnetic phase for alloys with x&amp;lt;0.7 is revealed. It is shown that in the region 0.5&amp;lt;x&amp;lt;0.8, ferromagnetism and antiferromagnetism can coexist in the low-temperature phase, which possesses spontaneous magnetization. This phase can be described as a canted ferromagnetic structure. The electronic structure of the alloy Mn1.5Fe0.5As0.5P0.5 is calculated in the ferromagnetic and nonmagnetic states. A comparison of the calculated and experimental values of the magnetic moment per formula unit shows that a pure ferromagnetic state is realized only in alloys with x&amp;gt;0.8, for which those values are in good agreement. A model is constructed that can describe correctly the main features of the spontaneous and magnetic-field-induced magnetically ordered states observed in the given system. The parameters of the model are the degree of filling of the d band, the nonmagnetic density of electronic states, and the interatomic exchange integral. Their values are estimated from the data of electronic structure calculations from first principles. The model has made it possible to predict and experimentally observe the existence of a triple point on the state diagram of these alloys.

Neutron diffraction study of the [formula omitted] ( [formula omitted], 0.7 and 1) compounds and the general description of the magnetic behavior of Mn in [formula omitted] and [formula omitted

The magnetic structures of the La 1 - x Pr x Mn 2 Si 2 ( x = 0.4 , 0.7 and 1) have been investigated by powder neutron diffraction between 2 and 308 K. According to magnetic measurements, the x = 0.4 sample shows a typical SmMn 2 Ge 2 -like magnetic behavior. Neutron diffraction indicates a canted antiferromagnetic structure below 130 K and a canted ferromagnetic structure above 240 K. Between 130 and 240 K, the canted ferromagnetic and antiferromagnetic structures coexist. Since the magnetic moments of Mn atoms, the unit cell parameters and the scale parameters of the canted antiferromagnetism and canted ferromagnetism are highly correlated between 130 and 240 K, a special refinement procedure was introduced. The critical Mn–Mn value was determined as 2.87 A ˚ , and the spontaneous volume change and linear magnetostriction are derived. Neutron diffraction revealed a canted antiferromagnetic structure for La 0.3 Pr 0.7 Mn 2 Si 2 . A canted antiferromagnetic structure was also detected for PrMn 2 Si 2 by neutron diffraction in contrast to previous reports of a collinear arrangement. The present results are compiled together with previous ones on RMn 2 Ge 2 and RMn 2 Si 2 (R: Y, La and rare-earth) compounds in two magnetic phase diagrams. These two graphics summarize the general magnetic behavior of Mn in the RMn 2 Ge 2 and RMn 2 Si 2 compounds.

Ga magnetic polarization in Mn3GaC under high pressure probed by Ga K-edge XMCD

To study pressure-induced ferromagnetic state in Mn3GaC perovskite, we have performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) spectroscopy at the Ga K-edge under high pressure up to 29.4 GPa at room temperature. Ga K-edge XMCD was observed under pressure ranging from 4.5 to 29.4 GPa and results indicate that the Ga atom is magnetically polarized under high pressure. From the XMCD spectral profile, it is suggested that the pressure-induced ferromagnetic state has a canted ferromagnetic structure.

Magnetic structures of the CeScSi-type RZrSb compounds (R = Tb, Er)

Investigations made by neutron diffraction experiments on the RZrSb compounds (R = Tb, Dy, Ho and Er) are reported. These compounds crystallize in the tetragonal CeScSi-type structure (space group I4/mmm, No. 139). Below T C (65 and 45 K for the Tb and DyZrSb compounds, respectively), the magnetic structure of both TbZrSb and DyZrSb compounds consists of ferromagnetic (0 0 1) layers staked along the c-axis ( μ Tb = 5.6(5) μ B and μ Dy = 4.6(5) μ B at 2 K). Below T C = 22(2) K, the magnetic structure of the HoZrSb compound consists of a canted ferromagnetic structure with M x = 1.02(5) μ B (an antiferromagnetic arrangement takes place in the a direction), M z = 5.01(8) μ B and M total = 5.11(8) μ B at 2 K. Below T N = 13 K, the ErZrSb compound adopts an incommensurate magnetic structure (antiferromagnetic) with a propagation vectors Q [±0.1580(6), 0, 0] and a total moment value of μ Er = 3.58(6) μ B at 2 K. The results are discussed and compared with those obtained for the closely related RTGe (R = Tb, Er, T = Ti, Mn, Ru) CeFeSi-type and CeScSi-type compounds.

Neutron diffraction study of the magnetic structures ofPrMn2−xCoxGe2 (x = 0.4,0.5 and 0.8) with a new refinement procedure

The magnetic structures of PrMn2−xCoxGe2 (x = 0.4, 0.5 and0.8) with ThCr2Si2-type structure have been investigated by means of neutron diffraction measurementsbetween 2 and 312 K. We introduced a new refinement procedure to determine the magneticmoments of Pr and Mn sublattices below the rare-earth ordering temperatureTCPr because of the overlapping of the magnetic reflections of the Pr and Mnsublattices. Rietveld refinements demonstrated that above the Curie temperaturean intralayer antiferromagnetic ordering within (001) Mn layers is observed inPrMn1.6Co0.4Ge2 andPrMn1.5Co0.5Ge2, while theintralayer antiferromagnetic ordering within (001) Mn layers is found over the whole temperature range forPrMn1.2Co0.8Ge2. Below the Curietemperature the PrMn1.6Co0.4Ge2 and PrMn1.5Co0.5Ge2 compounds have a canted ferromagnetic structure with the canting angles62° and65° at2 K, respectively. Below 75 and 70 K, a ferromagnetic ordering of the Pr sublattice is observed alongthe c-axis for these compounds. Below 70 K, a ferromagnetic ordering of Prsublattices is found (not detected by magnetic measurements) along thec-axisin PrMn1.2Co0.8Ge2.

Magnetic structure and transitions ofDy2Ni2Pb

We have studied the magnetic structure and magnetic properties of the orthorhombic compound ${\mathrm{Dy}}_{2}{\mathrm{Ni}}_{2}\mathrm{Pb}$ by means of neutron-diffraction and bulk measurements. The bulk measurements (susceptibility, resistivity, and specific heat) suggest two distinct magnetic phase transitions: one antiferromagnetic at ${T}_{N}=14.5\mathrm{K}$ and the other at ${T}_{m}=3.5\mathrm{K},$ below which a ferrimagnetic or canted ferromagnetic structure is anticipated. On the contrary, neutron-diffraction measurements, which were made in the range 1.5--20 K, showed that ${\mathrm{Dy}}_{2}{\mathrm{Ni}}_{2}\mathrm{Pb}$ has a complicated noncollinear antiferromagnetic spin structure in the whole temperature range studied. The magnetic structure is described by two commensurate propagation vectors ${\mathbf{q}}_{1}=(0,0,0)$ and ${\mathbf{q}}_{2}=(1/3,0,0)$ with Dy moments confined to the $a\ensuremath{-}c$ plane. A smooth development of ${\mathbf{q}}_{1}$ and ${\mathbf{q}}_{2}$ magnetic-moment components at low temperatures indicates that the magnetic structure remains antiferromagnetic. We attempt to reconcile both bulk and neutron results. The possibility of another order-order magnetic phase transition at lower temperature is suggested.