Juan Rodriguez-Carvajal

Institut Laue-Langevin · Diffraction

The mathematical structure, description and classification of magnetic space groups is briefly reviewed, with special emphasis on the recently proposed notation, the so-called UNI symbols [Campbell et al. (2022). Acta Cryst. A78, 99–106]. As illustrative examples, very simple magnetic space groups from each of the four possible types are described...

In recent decades, sustained theoretical and software developments have clearly established that representation analysis and magnetic symmetry groups are complementary concepts that should be used together in the investigation and description of magnetic structures. Historically, they were considered alternative approaches, but currently, magnetic...

A report from the International Union of Crystallography Commission on Magnetic Structures outlining the recommendations for communicating commensurate magnetic structures.

We report a comprehensive investigation into the magnetic and magnetoelectric characteristics of green phase compounds R2BaCuO5 (R=Er, Eu, Y, Tm, and Lu) through an array of experimental techniques, including dc magnetization, specific heat, dielectric, pyrocurrent, and neutron diffraction measurements. Our study reveals that all these compounds ex...

DOI:https://doi.org/10.1103/PhysRevB.105.099901

The two commonly used systems of magnetic space-group (MSG) symbols, with accompanying numbers and settings, are those of Belov–Neronova–Smirnova (BNS) and Opechowski–Guccione (OG). The symbols from both systems have been used for several decades now. Both have advantages and disadvantages. Both present challenges of interpretation to novice and ex...

The linear magnetoelectric effect and multiferroicity phenomena occur independently due to breaking inversion symmetry below the magnetically ordered state of either transition metal or rare-earth ions. Here, we report the occurrence of a linear magnetoelectric effect and magnetic field-induced ferromagnetism and ferroelectricity below TNR in the o...

Ferroelectric oxides have attracted much attention due to their wide range of applications, particularly in electronic devices such as nonvolatile memories and tunnel junctions. As a result, the monolithic integration of these materials into silicon technology and their nanostructuration to develop alternative cost-effective processes are among the...

SbPO4 is a complex monoclinic layered material characterized by a strong activity of the non-bonding lone electron pair (LEP) of Sb. The strong cation LEP leads to the formation of layers piled up along the a-axis and linked by weak Sb-O electrostatic interactions. In fact, Sb is 4-fold coordination with O similar to what occurs with the P-O coordi...

DOI:https://doi.org/10.1103/PhysRevResearch.2.049002

Ferroelectric oxides have attracted much attention due to their wide range of applications, especially in electronic devices such as nonvolatile memories, solar cells, and tunnel junctions. However, ferroelectrics are very few in nature and to achieve truly multifunctional oxide devices, these materials should be integrated in Silicon-based platfor...

In most of the spin-induced multiferroics, the ferroelectricity is caused by inversion symmetry breaking by complex spin structures of the transition-metal ions. Here, we report the importance of interplay of 4f−3d magnetic interactions in inducing ferroelectricity in the centrosymmetric (Pnma) green phase compound Gd2BaCuO5. With decreasing temper...

The origin of the metal-to-insulator transition (MIT) in RNiO3 perovskites with R = trivalent 4f ion has challenged the condensed matter research community for almost three decades. A drawback for progress in this direction has been the lack of studies combining physical properties and accurate structural data covering the full nickelate phase diag...

While ferromagnetism has been known since many centuries, more complex magnetic structures have only been identified in the twentieth century: ferrimagnetism, antiferromagnetism, helimagnetism, modulated structures… Incommensurable or long-period structures have first been deduced as consequences of phenomenological models, e.g., the Heisenberg Ham...

This report presents with one of the rare experimental studies on the magnetic structure of hybrid framework materials: [C(ND2)3]Me²⁺(DCOO)3 (Me = Cu, Mn and Co) by using neutron powder diffraction. The copper guanidinium formate (CuGF), having a polar structure is a promised multiferroic member of the hybrid perovskite metal guanidinium formates a...

We investigate the emergence of the charge order in PrNiO$_3$ below the metal-insulator transition using high resolution neutron powder diffraction data analyzed in terms of symmetry-adapted distortion modes. Our analysis allows to identify the contribution of the different modes to the global distortion in a broad temperature range (10-300K), and...

DOI:https://doi.org/10.1103/PhysRevB.97.019905

The A-site cation-ordered spinel LiFeCr4O8 is a unique system which manifests properties of the frustrated pyrochlore lattice, including the breathing distortion and antiferromagnetic coupling between A and B sites. This compound crystallizes in a cubic spinel structure with a noncentrosymmetric space group (F4¯3m), where Li+ and Fe3+ ions are orde...

We report the discovery of magnetoelectric multiferroicity in a family of oxides, RFeWO6 (R=Dy, Eu, Tb, and Y) that crystallize in a polar aeschynite-type structure (Pna21) with an ordered arrangement of Fe3+ and W6+ ions. Magnetization and analysis of neutron-diffraction data of DyFeWO6 reveal a commensurate noncollinear antiferromagnetic ordering...

CePd2Al2−xGax compounds crystallizing in the tetragonal CaBe2Ge2-type structure (space group P4/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 CePd2Al2 is described by an incommensurate propagation ve...

This paper presents the physical properties of a nonstandard orthorhombic form of MnV2O6 , including a comparison with the isostructural orthorhombic niobate MnNb2O6, and with the usual MnV2O6 monoclinic polymorph. Orthorhombic (Pbcn) Mn2O6 is obtained under extreme conditions of high pressure (6.7 GPa) and high temperature (800 ºC). A negative Cur...

Short-range structural and magnetic order in rapidly solidified nanostructured Ag100 − xMnx alloys featuring nominal large Mn content (x = 25, 32, 40 at.%), well above the maximum equilibrium concentration (x ~ 14 at.%), are quantified using X-ray, neutron and magnetic probes. These inhomogenous alloys contain coexisting Mn-rich and Mn-deficient na...

The technological impact of combining substrate technologies with the properties of functional advanced oxide ceramics is colossal given its relevant role in the development of novel and more efficient devices. However, the precise control of interfaces and crystallization mechanisms of dissimilar materials at the nanoscale needs to be further deve...

The structures and magnetic properties of the antiferromagnetic hexagonal pseudo ternary compounds HoMn6−xCrxGe6 (x=1, 1.5 and 2) are studied by neutron diffraction in the temperature range 1.5–300 K. The substitution of nonmagnetic Cr for Mn greatly affects the magnetic properties of HoMn6Ge6 by reducing the ordering temperature from 466 K to 278...

The remarkable intrinsic magnetic properties of the LaFe12B6 compound have been studied by neutron powder diffraction (NPD) and magnetization measurements. The NPD measurement reveals that LaFe12B6 exhibits an antiferromagnetic (AFM) structure that can be described with a magnetic propagation vector of (¼, ¼, ¼) below TN. In the amplitude-modulated...

We have reinvestigated the crystal structure of the low-dimensional fluoride $\beta$-FeF$_3(H_2O)_2\cdot$H$_2$O using high resolution neutron and X-ray diffraction data. Moreover we have studied the magnetic behavior of this material combining medium resolution and high flux neutron powder diffraction together with magnetic susceptibility measureme...

The combination of standard wafer-scale semiconductor processing with the properties of functional oxides opens up to innovative and more efficient devices with high value applications that can be produced at large scale. This review uncovers the main strategies that are successfully used to monolithically integrate functional complex oxide thin fi...

We present a neutron scattering study of the chromate spinel LiInCr4O8, which realizes a "breathing" pyrochlore lattice of S=32 spins. High-resolution neutron diffraction reveals a phase separation into a mixture of minority cubic and majority tetragonal phases below 18 K, followed by apparent magnetic order in a complex two-up two-down pattern in...

Understanding the crystallization of enantiomorphically pure systems can be relevant to diverse fields such as the study of the origins of life or the purification of racemates. Here we report on polycrystalline epitaxial thin films of quartz on Si substrates displaying two distinct types of chiral habits that never coexist in the same film. We com...

Motivated by the recent observations of incommensurate magnetic order and electric polarization in YBaCuFeO5 up to temperatures TN2 as high as 230K [1,2] we report here for the first time a model for the incommensurate magnetic structure of this material that we complement with ab-initio calculations of the magnetic exchange parameters. Using neutr...

We developed an original strategy to produce vertical epitaxial single crystalline manganese oxide octahedral molecular sieve (OMS) nanowires with tunable pore sizes and compositions on silicon substrates by using a chemical solution deposition approach. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates com...

The combination of standard wafer-scale semiconductor processing with the properties of functional oxides opens up to innovative and more efficient devices with high value applications which can be produced at large scale. This review uncovers the main strategies that are successfully used to monolithically integrate functional complex oxide thin f...

Complex 3D macrostructured nanoparticles are transformed from amorphous silica into pure polycrystalline α-quartz using catalytic quantities of alkaline earths as devitrificants. Walls as thin as 10 nm could be crystallized without losing the architecture of the particles. The roles of cation size and the mol% of incorporated devitrificant on cryst...

High resolution neutron diffraction measurements have been carried out to characterize the crystallographic phases present in different Oxide Dispersion Strengthened (ODS) steels of interest for fusion technology. The different lattice structures, Im3m for the ferritic ODS and Fm3m for the austenitic ODS, are resolved showing line anisotropy effect...

Quartz has been widely used as a bulk material in optics, the microelectronic industry, and sensors. The nanostructuring and direct integration of oriented quartz crystals onto a semiconductor platform has proven to be challenging. However, here, a new approach is presented to integrate epitaxial quartz films with macroperforations within the range...

Magnetic Crystallography is a sub-field of Crystallography concerned with the description and determination of the magnetisation density in solids. A magnetic structure corresponds to a particular spatial arrangement of magnetic moments that sets up below the ordering temperature. The determination of magnetic structures is mainly done using neutro...

Ferroelectric materials have been known for almost one century [1]. While their potential for applications was rapidly recognized, the possibility of combining ferroelectricity with magnetic order -preferably with ferromagnetism- has resulted in an enormous deal of interest during the last decade. Several new materials combining both types of order...

A novel cobalt(II) complex of formula [Co2(cbut)(H2O)3]n (1) (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid) has been synthesized under hydrothermal conditions and its crystal structure has been determined by means of synchrotron radiation and neutron powder diffraction. The crystal structure of 1 consists of layers of cobalt(II) ions extending...

TmFe4Ge2 undergoes a double magneto-elastic first order transition at TN,Tc where the high temperature (HT) tetragonal phase disproportionate into two distinct orthorhombic low temperature (LT) phases with commensurate and incommensurate magnetic wave vectors respectively: P42/mnm(HT)TN,Tc→Cmmmq1=(0,12,0)+Pnnm(q2=(0,qy,0),qy≈2/11(LT) Neutron diffr...

R2RhIn8 compounds (space group P4/mmm, R is a rare-earth element) belong to a large group of structurally related tetragonal materials which involves several heavy-fermion superconductors based on Ce. We have succeeded to grow single crystals of compounds with Nd, Dy and Er and following our previous bulk measurements, we performed neutron-diffract...

In this paper, we report on the structural and magnetic properties, as deduced from susceptibility measurements and neutron powder diffraction experiments, of an orthorhombic nickel disulfate, Li2Ni(SO4)2. This phase presents NiO6 octahedra linked via SO4 groups only, leading to an antiferromagnetic behavior resulting from super-super-exchange inte...

We developed an original strategy to produce vertical epitaxial single crystalline manganese oxide octahedral molecular sieve (OMS) nanowires with tunable pore sizes and compositions on silicon substrates by using a chemical solution deposition approach. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates com...

The exchange mechanism and magnetic structure of the organic-inorganic layered molecule-based magnet [Co2(bta)]n (1) (H4bta =1,2,4,5-benzenetetracarboxylic acid) have been investigated through variable-temperature magnetic susceptibility measurements and supported with a series of neutron diffraction experiments. Cryomagnetic studies have shown an...

The ferroic phase transition in LaEr(MoO4)3 has been analyzed for the first time. It has been confirmed that this compound undergoes a phase transition from a tetragonal system (paraelectric-paraelastic phase), with space group P-421 m [β-Gd2(MoO4)3 averaged phase] to an orthorhombic system (ferroelectric-ferroelastic phase), with space group Pba2...

Two polymorphs of Holmium molybdate, known as β'-phase and γ-phase, were prepared by solid state reaction with different thermal treatments. These polycrystalline samples have been studied for the first time by X-ray thermodiffractometry from room temperature up to 1300 K. We found that the initial β'-phase undergoes a transition to a β-phase and t...

New materials initially designed for battery electrodes are often of interest for magnetic study, because their chemical compositions include 3d transition metals. We report here on the magnetic properties of marinite phases Li2M(SO4)2 (M = Fe, Co, Mn) and Li1Fe(SO4)2, which all order antiferromagnetically at low temperature. From neutron powder di...

Fabricating Quartz Quartz is used industrially as an abrasive, as an inert glassy material, or for high-quality crystals in microelectronics. It is also valued for its piezoelectronic properties. However, it is hard to grow quartz as a patterned material or to integrate it into nanostructured devices. Carretero-Genevrier et al. (p. 827 ; see the Pe...

The magnetic structures of the GdNi1-xCux orthorhombic compounds are presented for x=0, 0.3 and 0.6. The two first are ferromagnetic with the magnetic moments along the b direction, whereas GdNi0.4Cu0.6 orders in a helimagnetic structure with a propagation vector (0,0,1/4), the magnetic moments lying in the (ab) plane. The structures are discussed...

An analysis of the crystallographic structures of CeNixPt1−x and the diluted compounds with substitutions of Ce by La or Y is presented. The relationship between the different sample preparation methods and some structural features, such as the existence of two phases in some of the compounds, have been also stressed. From the magnetic intensities,...

The system Bi2(n+2)Mon O6(n+1) is described with the superspace formalism. Considering the cationic distribution of the member with n=3, a superspace model is constructed beginning with a model previously proposed for the compound Bi2MoO6. The description of even members requires additional modifications. As a result, two superspace models are prop...

Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH2(CH3)2]n[FeIIIFeII(HCOO)6]n. The crystal structure at 220 K has been refined from Laue diffraction data, while the crystal structure at 45K,...

The magnetic structure of the tetragonal antiferromagnetic LuFe4Ge2 and YFe4Si2 compounds has been studied by high resolution neutron and X-ray diffraction above and below the magneto-elastic transition at T-N, T-C = 32 K and 76 K, respectively. Below T-N,T-C the tetragonal high temperature (HT) phase transforms into the low temperature (LT) orthor...

Mechanical milling of magnetic alloys 3d-(Fe) and 4f-based (Tb) results in the promotion of magnetic disorder. In Fe22Cu14Ag64 the nanoscopic arrangement has been revealed by a very comprehensive mult-ipattern Rietveld analysis using a combination of four sets of data including X-ray and neutron diffraction. The nanostructure is formed by Fe61Cu39...

The system Bi2(n + 2)MonO6(n + 1) is described within the superspace formalism. Two superspace models are proposed for the different members of this family, depending on the parity of the parameter n. The superspace model for the odd members is constructed through the embedding of the cationic distribution of the member with n = 3, and the modifica...

NaFeSO4F and NaCoSO4F crystallize in the maxwellite crystal structure and consist of one-dimensional chains of corner-sharing MO4F2 octahedra linked together through F atoms sitting in a trans configuration with respect to each other. Magnetic susceptibility measurements and low-temperature powder neutron diffraction indicate that both the Fe- and...

The crystallographic approach to magnetic structures is largely based on two kinds of descriptions: symmetry invariance of magnetic configurations (Magnetic Space Groups, often called Shubnikov groups) and group representation theory applied to conventional crystallographic space groups. The first approach is nearly exclusively used for the case of...

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=25 K and undergo first-order magnetic transitions at T-ic = 16.5 K. Their T-phase diagrams comprise a low tempera...

Neutron diffraction has unique capabilities for scientific research under extreme conditions, mainly in two large areas: crystallography/geosciences and magnetism/solid-state physics. The growing interest in these fields is attested by the quantity and quality of publications, by the number of experiments proposed at the different neutron sources a...

Neutron diffraction techniques have been used to determine the low temperature crystal structure and to shed light on the magnetic behavior of the [Mn(3)(suc)(2)(ina)(2)](n) (suc = succinate and ina = isonicotinate) complex. The ferromagnetic signal observed below T(c) ≈ 5 K in this compound is due to a noncompensation of homometallic spins in the...

The Sc2(WO4)3-type phase (Pbcn) of Y2(MoO4)3, Er2(MoO4)3 and Lu2(MoO4)3 has been prepared by the conventional solid-state synthesis with preheated oxides and the negative thermal expansion (NTE) has been investigated along with an exhaustive structural study, after water loss. Their crystal structures have been refined using the neutron and x-ray p...

Pure titania (TiO 2 ) polycrystalline thin films in rutile, anatase and mixed phase have been grown on amorphous glass substrates by pulsed laser deposition method at various oxygen gas pressure. Wettability investigations have been carried out on these films. Consistent with our previous report [J. Phys. D: Appl. Phys. 41, 155308 (2008)] it has be...