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The magnetic structure of chromium arsenide CrAs is studied with neutron powder diffraction at ambient pressure in the temperature range 1.5–300 K as well as with neutron single‐crystal diffraction at 2 K and 0.12 GPa. The material undergoes an anti‐isostructural phase transition at TN = 267 K and atmospheric conditions, in which both orthorhombic phases have the same space‐group symmetry (Pnma, Z = 4) but different distortions of the parent hexagonal structure of the NiAs type (P63/mmc, Z = 2). The magnetic structure below TN is incommensurate with the propagation vector k = (0, 0, kc). At ambient pressure, the component kc decreases from kc = 0.3807 (7) at 260 K to kc = 0.3531 (6) at 50 K. Below this temperature, it is basically constant. With increasing pressure at 2 K, kc is also constant within standard uncertainties [kc = 0.353 (2)]. For the analysis of the magnetic structure, a group‐theoretical approach based on the space group of the nuclear structure and its subgroups is used. To avoid falling into false minima in the refinements, a random search for magnetic moments in the models is implemented. In the literature, the magnetic structure has been determined on the basis of powder diffraction data as a double helix propagating along the c axis. Although this double‐helical model leads to satisfactory agreement factors for our powder data, it does not reproduce the intensities of the magnetic satellite reflections measured on single‐crystal data in a satisfactory way and can therefore be discarded. Instead, several other models are found that lead to better agreement. Each of them is spiral‐like with directional components in all three directions and with no spin‐density wave character that would cause a non‐constant magnetic moment. In all these models, the ordering of the spins is neither a pure helix nor a pure cycloid. Instead, the unit vectors of the spin rotation planes make an angle α, 0° < α < 90°, with respect to the c* direction. The model in superspace group P21.1′(α0γ)0s yields the best agreement factors in the refinements of the neutron single‐crystal and powder diffraction data. This model is unique as it is the only one in which all the magnetic moments rotate with the same chirality. [ABSTRACT FROM AUTHOR]

A new double double perovskite of ideal composition CaMnCoWO6 has been synthesised at high pressure. The structure is tetragonal (P42/n, a=7.6651(3), c=7.6822(3) Å) and disorder between A‐site Mn2+ and B‐site Co2+ leads to a Co‐rich off‐stoichiometric composition CaMn0.8Co1.2WO6 [Ca(Mn0.65Co0.35) (Co0.86Mn0.14)WO6]. An unusual combination of commensurate and incommensurate spin orders (A‐site Mn/Co spins with propagation vector (0.5 0.5 0.5) and B‐site Co/Mn spins with (0.5 0.42 0.5)) is observed below a magnetic transition at TC=18 K. This is the first discovery of complex magnetism in the double double perovskite family. [ABSTRACT FROM AUTHOR]

A new double double perovskite of ideal composition CaMnCoWO6 has been synthesised at high pressure. The structure is tetragonal (P42/n, a=7.6651(3), c=7.6822(3) Å) and disorder between A‐site Mn2+ and B‐site Co2+ leads to a Co‐rich off‐stoichiometric composition CaMn0.8Co1.2WO6 [Ca(Mn0.65Co0.35) (Co0.86Mn0.14)WO6]. An unusual combination of commensurate and incommensurate spin orders (A‐site Mn/Co spins with propagation vector (0.5 0.5 0.5) and B‐site Co/Mn spins with (0.5 0.42 0.5)) is observed below a magnetic transition at TC=18 K. This is the first discovery of complex magnetism in the double double perovskite family. [ABSTRACT FROM AUTHOR]

Magnetic fluids based on single-domain magnetic spinel ferrite nanoparticles dispersed in various liquid media are of particular practical and scientific interest. This paper presents a muon spectroscopy study of a ferrofluid based on magnetic nanoparticles of CoFe2O4 molecules dispersed in water (H2O) with a nanoparticle concentration of 3%. In this study, it was determined that the structure and magnitude of the magnetization of a ferrofluid depend on the viscosity of the liquid itself. It was shown that, at room temperature (290 K) and under an external magnetic field of 527 G, the observed additional magnetization was ~20 G. In a small fraction of the sample under study (~20%), negative magnetization (diamagnetism) was observed. At low temperatures (~30 K), the sample acted as a paramagnet in a magnetic field. For the first time, the magnetic field inside and in the immediate vicinity of a CoFe2O4 nanoparticle has been measured experimentally using the μSR method: the value was 1.96 ± 0.44 kG; thus, direct measurement of the magnetization of a nanoscale object was performed. [ABSTRACT FROM AUTHOR]

Magnetic fluids based on single-domain magnetic spinel ferrite nanoparticles dispersed in various liquid media are of particular practical and scientific interest. This paper presents a muon spectroscopy study of a ferrofluid based on magnetic nanoparticles of CoFe2O4 molecules dispersed in water (H2O) with a nanoparticle concentration of 3%. In this study, it was determined that the structure and magnitude of the magnetization of a ferrofluid depend on the viscosity of the liquid itself. It was shown that, at room temperature (290 K) and under an external magnetic field of 527 G, the observed additional magnetization was ~20 G. In a small fraction of the sample under study (~20%), negative magnetization (diamagnetism) was observed. At low temperatures (~30 K), the sample acted as a paramagnet in a magnetic field. For the first time, the magnetic field inside and in the immediate vicinity of a CoFe2O4 nanoparticle has been measured experimentally using the μSR method: the value was 1.96 ± 0.44 kG; thus, direct measurement of the magnetization of a nanoscale object was performed.

We present the susceptibility and neutron diffraction data on multiferroic Ni 3− x Co x V 2 O 8 with x =0.1 and 0.5. The temperature dependence of the susceptibility indicates that the magnetic order–disorder transition occurs at T HTI =8.5 K in both samples. Below T HTI , the high-temperature incommensurate magnetic structure is realized, which undergoes a transition to the low-temperature incommensurate phase when the sample is cooled. The temperature evolution of the propagation vector k for x =0.1 is very weak, which confirms previous studies showing that substitution of 3.5% Ni ions by Co ions suppresses the explicit temperature dependence of k that is observed in the parent compound. On the other hand, we found that the vector k for x =0.5 exhibits a definite temperature dependence, which differs from the case of the undoped sample ( x =0). [ABSTRACT FROM AUTHOR]

We have synthesized the R 5 Pb 3 ( R =Gd–Tm) compounds in polycrystalline form and performed neutron scattering and magnetization measurements. For all R 5 Pb 3 reported here the Weiss temperatures θ W are several times smaller than the ordering temperatures T ORD , while the latter are remarkably high ( T ORD up to 275 K for R =Gd) compared to other known R – M binaries ( M =Si, Ge, Sn and Sb). The magnetic order changes from ferromagnetic (FM) in R =Gd, Tb to antiferromagnetic (AFM) in R =Dy–Tm. Below T ORD , the magnetization measurements together with neutron powder diffraction show complex magnetic behaviors and reveal the existence of up to three additional phase transitions, believed to be a result of large anisotropic exchange and/or crystal electric field effects, induced high anisotropy. The R 5 Pb 3 magnetic unit cells for R =Tb–Tm can be described with incommensurate magnetic wave vectors with spin modulation either along the c axis in R =Tb, Er and Tm, or within the ab plane in R =Dy and Ho. [ABSTRACT FROM AUTHOR]

The compound ScMn6Ge6 (HfFe6Ge6-type, P6/mmm) orders antiferromagnetically below TN=516 K. Neutron powder diffraction at various temperatures 1.5-309 K shows the existence of two distinct magnetic ordering ranges described by the commensurate q1=(0, 0, 1/2) and the incommensurate q2=(0, 0, qz) vectors: (i) the HT (high temperature) Tt≈100 KT>1.5 K range has an easy double-cone incommensurately modulated structure described by two vectors (q1, q2). At 1.5 K q2=(0, 0, 0.405(1)), the spiral angle is Φ=145.8° the cone half angle is α≈8° and the ordered moment value μMn=2.12(2) μB is the same as for the isomorphic RMn6Ge6 (R=heavy rare earth) compounds. The 1.5 K q2 satellites are very weak as the in-plane moment component measures only 0.31 μB. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties of a mixed inter-metallic compound, Tb0.95Er0.05Ni5, were investigated using a neutron diffraction method at low temperatures. These compounds were known to have a successive magnetic phase transition from the paramagnetic state at high temperature to a lock-in phase at low temperature through intermediate phases, i.e., PM(paramagnetic)–FM(ferromagnetic)–IC(incommensurate)–L(lock-in) in reverse order of temperature. A meta-magnetic phase transition between an IC phase and a FM phase at 9K was observed with the critical field, H MT~200mT. A new magnetic phase between the new phase (lock-in phase) and an IC phase has been observed. From the field dependence of the Bragg reflections and their satellite peaks at low temperatures (3–12K), weak field driven first-order magnetic phase transitions were recorded at six fixed temperatures. The critical magnetic field decreases exponentially with the temperature. From these experimental results, we obtained a magnetic phase diagram of Tb0.95Er0.05Ni5 at a low temperature region for the first time. [Copyright &y& Elsevier]

Abstract: The TbNi5 compound shows an interesting magnetic phase transition with an incommensurate structure below 23K, whose true nature remains unresolved. In order to solve this question, we have carried out polarized neutron diffraction experiments by measuring temperature and field dependence of the intensities of satellites and Bragg reflections. From the temperature dependence of both satellite peaks and Bragg reflection, we demonstrated that it has only one magnetic structure at a given temperature. Furthermore, unlike previous reports, we found that both ferromagnetic and modulated components of the Tb ion magnetic moments should be collinear to each other. Our data also show strong depolarisation effects that are most likely to arise from domain structure of ferromagnetic component. A critical field, which destroyers a modulated magnetic structure is found to be lower than a field value to saturate the ferromagnetic component, in which the intensity of Bragg ferromagnetic reflections reaches saturation. [Copyright &y& Elsevier]

Abstract: The temperature magnetic phase diagrams of the dimorphic HoSi compound were studied by neutron diffraction. The sample comprises 35.5% CrB- (Cmcm) and 64.5% FeB-type (Pnma) of structure. Both phases order antiferromagnetically below T N =25K and undergo first-order magnetic transitions at T ic =16.5K. Their T-phase diagrams comprise a low temperature (LT) 2.7K−T ic and a high temperature (HT) range T ic −T N with distinct wave vectors. The LT magnetic ordering of the CrB-type HoSi with the wave vector q 1=(1/2, 0, 1/2) corresponds to a uniaxial magnetic structure, with the Ho moments along the shortest axis c. At 2.7K the ordered moment value is 8.6(2)μB/Ho atom. The HT ordering, described by the wave vector q 2=(q 2x , 0, q 2z ) with a T-variable length, corresponds to an amplitude modulated structure. The magnetic ordering of the FeB-type HoSi requires two symmetry independent vectors q 3=(0, q 3y , q 3z ) for the LT- and q 4 =(q 4x , q 4y , 0) for the HT range. Both vectors correspond to sine wave modulated structures with the Ho magnetic moments confined along the shortest axis b. The q 3 vector has an almost invariable length vs. T close to ≈(0, 9/17, 1/11). At 2.7K the amplitude of the wave is 10.9(1)μB/Ho atom. At T ic q 3 jumps to the wave vector q 4 =(q 4x , q 4y , 0) with a T-variable length. At 17K q 4 =(0.092(1), 0.538(3), 0). Around T ic there is a narrow coexistence range of the q 3 and q 4 competing phases. Various models are discussed and compared with the isomorphic RSi (R=rare earth) compounds counterparts of HoSi, a comparison that has led us to briefly review the magnetic structures available in the literature for this interesting class of compounds. [Copyright &y& Elsevier]

Abstract: The crystallochemical and magnetic nature of ternary Sc1+δ Fe4−δ Al8 intermetallic with a small Sc excess δ=0.1 was investigated by scanning electron microscope, X-ray powder diffraction, neutron diffraction, Mössbauer effect and superconducting quantum interference device techniques. The sample crystallizes in a tetragonal ThMn12 type structure. The excess of Sc atoms substitute Fe at the (8f) positions and have a pronounced effect on the magnetic properties. The experiments carried out in temperature range 4–320K show that below 120K the magnetic structure of the alloy forms a double cycloid with magnetic moments rotating according to the incommensurate in-plane wave vector, which is temperature independent up to 160K. The value of Fe magnetic moment is close to 0.9μB atom−1 at 4K. Temperature dependence of unit cell dimensions can be explained within the Debye–Grüneisen approximation. [Copyright &y& Elsevier]

Abstract: The temperature magnetic phase diagrams, of the dimorphic DySi compound, have been studied in terms of wave vectors in the range 1.5–45K, by neutron diffraction. The polycrystalline sample consists of 26% of CrB-type (Cmcm no. 63, all atoms at 4c site: (0, y, 1/4)) and of 74% of FeB-type (Pnma no. 62, all atoms at 4c site: (x, 1/4, z)). The CrB-ordering is described by the wave vector: q 1=(0, 0, 1/2) over the entire magnetically ordered regime with a uniaxial magnetic structure along the shortest axis c. The FeB-type magnetic phase diagram reveals three distinct regions of magnetic ordering below T N and one first order transition at T 2=23.5K (on heating). The ordering is described by two symmetry independent magnetic vectors q 2=(0, 1/2, 1/6) and q 3=(0, q 3 y , q 3 z ) with a temperature variable length. At 1.5K q 3 y ≈1/2 and q 3 z ≈1/11. The two phases coexist in the form of domains. They differ in the moment orientation of the q 3 phase that deviates by ∼22° from the b-axis in the (0, 0, 1) plane. The low temperature range (LT) 1.5K—T 2 subdivides into two regions: (i) LT-1, between 1.5K—T 1 where the relative amount of the two phases remains unchanged and in (ii) LT-2: T 1–T 2 where the amount of the incommensurate q 3 phase increases at the cost of the commensurate q 2 amplitude modulated structure which remains unchanged but fully disappears at the first order transition at T 2=23.5K. The q 3 phase undergoes minor changes until 22K and gets destabilised at T 2 where the q 3 z component jumps from the LT value q 3 z ≈1/11 to the HT value ≈1/7 and the q 3 y component increases from 0.484(1) to 0.495(1). (iii) The high temperature (HT) range T 2–T N (T N=40±1K) is described by a single wave vector q 3. The disproportionation of the HT magnetic phase q 3 below T 2 into two coexisting distinct phases q 2, q 3 down to 1.5K is an unusual phenomenon, to our knowledge observed for the first time. Various mechanisms are discussed. [Copyright &y& Elsevier]

The dipolar magnetic field distribution at the muon site was calculated for a single k incommensurate magnetic structure using Monte Carlo simulation. It is shown that the generated dipolar magnetic field vectors lie on a plane, their ends defining an ellipse. With this information, a simple analytical formula for the field distribution at the muon site was computed. [ABSTRACT FROM AUTHOR]

Abstract: The low-temperature magnetic ordering of the dimorphic DySi compound has been studied at 1.5K by neutron diffraction on two polycrystalline samples. The samples comprise various amounts of the two orthorhombic modifications: CrB-type (Cmcm Nr. 63, all atoms at 4c site: (0, y, )) and FeB-type (Pnma Nr. 62, all atoms at 4c site: (x, , z)), both order antiferromagnetically (T N≈38K). The CrB-type phase orders with a uniaxial structure with the wave vector q 1=(0, 0, ) requiring a doubling of the c-axis. The Dy moments point along the linear chain with the shortest distance c. At 1.5K, the ordered moment value is 8.57(1)μB/Dy atom. Two symmetry independent wave vectors describe the 1.5K magnetic ordering of the FeB-type phase: q 2=(0, , ) and q 3=(0, 0.484(1), 0.0892(1)), coexisting in form of domains. In both structures the magnetic moments are confined to the (001) plane at an angle of 2(2)° and 22(3)° from the shortest axis b, respectively. Both structures correspond to sine wave modulations. The amplitude of the q 2 wave is mo =7.5(1)μB/Dy atom and that of q 3 8.2(1)μB/Dy atom. The wave vector q 2 when referring to the (a, 2b, c) cell and the wave vector q =(0, 0, ) corresponds to a transversal modulation, which by a proper origin choice can be also described as an antiphase domain structure with two amplitudes. The moments point to the b-axis and are stacked in the sequence (+mo /2, −mo /2, −mo , −mo /2, +mo /2, +mo , …) along the c-direction, while tb acts as an antitranslation. For the q 3 phase, the local moment value depends on the atom position in the wave. We also discuss the case where q 3 and q 2 act simultaneously in physical space. [Copyright &y& Elsevier]

Unpolarized neutron diffraction and magnetization experiments have been performed on single crystal of ScFe4Al8 intermetallic compound. In the single crystal both, neutron and high resolution X-ray diffraction measurements, indicate perfect crystallochemical order. The magnetic ordering was studied in the temperature range 8-250 K. LT neutron measurements show that the compound exhibits magnetic spiral structure. The scandium seems magnetically inactive while the iron site splits into two independent magnetic orbits. Below 115 K two sets of magnetic reflections were found. Each of them requires different wave vector representation i.e. [image omitted] and [image omitted] and discloses different temperature behavior. In the basic elementary cell, the Fe moments of adjacent atoms along c axis are forming a constant angle while along the face diagonals the mutual orientation of magnetic moments is almost antiparallel. The iron moments rotate within the basal plane upon entering the neighboring cell. The magnetic structure with two modulation vectors is different from the one observed earlier by means of magnetic neutron powder diffraction, where only one modulation vector was observed. The reasons of this different magnetic behavior are discussed. [ABSTRACT FROM AUTHOR]

At 2 K the magnetic propagation vector has a kz=0.2593(4) c* component and the dysprosium magnetic moments directions form a cone with its axis making an angle of 35° with the c-axis of the crystal. Their amplitudes are 7.9 and 4.5 μB for the 4d and 6 g sites, respectively. Neutron diffraction and susceptibility measurements on a powdered Dy5Si3 compound, crystallizing in space group P63/mcm, indicate an incommensurate magnetic structure with Nee´l temperature equal to 125 K. [Copyright &y& Elsevier]

High resolution and high intensity neutron powder diffraction is used to study the ground state magnetic order and the spin reorientation transition in the orthoferrite DyFeO 3 . The transition from the high temperature k = 0 Γ 4 ( G x A y F = 4 K the Dy-sublattice orders in an incommensurate magnetic structure with z ) to the low temperature Γ 1 ( A x G y C z ) type order of the Fe-sublattice is found at T SR = 73 K and does not show any thermal hysteresis. Below T N2 = 4 K the Dy-sublattice orders in an incommensurate magnetic structure with k = [0, 0, 0.028] while the Fe-sublattice keeps its commensurate Γ 1 type order. DyFeO 3 is the first orthoferrite R FeO 3 to possess an incommensurate magnetic order of the rare earth sublattice under zero field conditions; an important piece of information neglected in the recent discussion of its multiferroic properties., (© 2022 IOP Publishing Ltd.)

Abstract: On the example of a crystal with point symmetry group and based on the method of integral rational basis of invariants, linear and nonlinear invariants of first spatial derivatives with respect to the order parameters of the exchange origin have been calculated. It is shown the competition of what kind of parameters can initiate modulated magnetic structures in crystals of this symmetry. [Copyright &y& Elsevier]

Abstract: We investigated successive phase transitions in at and by means of resonant X-ray diffraction. A strong resonant diffraction signal is observed at the 101 reflection below at the Sm edge, whereas in the intermediate phase signals appear at incommensurate positions , where . Accordingly, the transition at is found to be a commensurate-to-incommensurate magnetic phase transition. [Copyright &y& Elsevier]

Abstract: The wave number dependence of RKKY multipolar interactions is derived for the Anderson-type model with orbital degeneracy in the simple cubic lattice. With the spherical Fermi surface and one conduction electron per cell, the Kohn anomaly arises in the magnetic interaction near the point of the Brillouin zone. This result may be relevant to the incommensurate magnetic structure observed in the quasi-cubic compound . [Copyright &y& Elsevier]

Abstract: Multiferroic ground states with a spatially modulated antiferromagnetic structure and electric polarization have been revealed in Eu1− x Y x MnO3 () single crystals. While the slightly substituted () compounds exhibited a transition from the incommensurate (IC) to the canted antiferromagnetic (CAF) state at , the transitions from IC to commensurate ferroelectric (C/FE) phase were observed at for . Various phase transitions were observed in the magnetic fields up to 250kOe along a, b, c axes by magnetization, magnetostriction and electric polarization measurements which show an existence of a spontaneous electric polarization below T lock. [Copyright &y& Elsevier]