Helical screw type magnetic structure of the multiferroic CaMn7O12 with low Cu-doping

2012 ◽  
Vol 68 (3) ◽  
pp. 240-249 ◽  
Author(s):  
W. Sławiński ◽  
R. Przeniosło ◽  
I. Sosnowska ◽  
V. Petříček
Keyword(s):  
Crystal Structure ◽  
Synchrotron Radiation ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Powder Diffraction Data ◽  
Atomic Position ◽  
Cu Doping ◽  
Vector Length ◽  
Modulation Vector ◽  
Modulation Length

The modulated crystal structure and modulated magnetic ordering of the multiferroic CaCu x Mn7−x O12 is studied by analysing neutron and synchrotron-radiation (SR) powder diffraction data with a model based on the magnetic superspace group R31′(00γ)ts. Both atomic position modulations and magnetic modulations are described with the modulation vector (0, 0, q). The magnetic ordering is a screw-type circular helix where the magnetic moments are perpendicular to the c direction. The temperature dependence of the modulation vector length and the ordered magnetic moments of Mn3+ and Mn4+ ions is given between T = 50 K and the Néel temperature T N ≃ 90 K. The atomic position modulation length L p and the magnetic modulation length L m fulfil the relation L m = 2L p at all temperatures between 50 K and T N.

The magnetic structure of braunite Mn2+Mn3+6O8/SiO4

1998 ◽  
Vol 213 (1) ◽  
Author(s):  
S. Ohmann ◽  
I. Abs-Wurmbach ◽  
N. Stüßer ◽  
T. M. Sabine ◽  
K. Westerholt
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
Neutron Powder Diffraction Data ◽  
Weakly Coupled

AbstractNeutron powder diffraction data of braunite MnThe magnetic structure is dominated by the magnetic ordering of the A layers thus reflecting the relations of the chemical cell: Within the (001) plane of the A sheets magnetic moments of the two nonequivalent MnMagnetization experiments indicate that besides the afordered Mn ions weakly coupled spins ordering at temperatures below 2 K exist. In accordance with that, additional neutron diffraction reflections arise at

Crystal structure refinement of α-Si3N4using synchrotron radiation powder diffraction data: unbiased refinement strategy

2000 ◽  
Vol 33 (1) ◽  
pp. 95-102 ◽  
Author(s):  
H. Toraya
Keyword(s):  
Crystal Structure ◽  
Synchrotron Radiation ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Structure Refinement ◽  
High Angular Resolution ◽  
Powder Diffraction Data ◽  
Counting Statistics

The crystal structure of α-silicon nitride (Si3N4) was refined by the Rietveld method using synchrotron radiation powder diffraction data (wavelength = 1.2 Å) collected at station BL-4B2 in the Photon Factory. A refinement procedure that adopted a new weight function,w= 1/Y_o^e (Yois the observed profile intensity ande≃ 2), for the least-squares fitting [Toraya (1998).J. Appl. Cryst.31, 333–343] was studied. The most reasonable structural parameters were obtained withe= 1.7. Crystal data of α-Si3N4: trigonal,P31c,a= 7.75193 (3),c= 5.61949 (4) Å,V= 292.447 (3) Å3,Z= 4;Rp= 5.08,Rwp= 6.50,RB= 3.36,RF= 2.26%. The following five factors are considered equally important for deriving accurate structural parameters from powder diffraction data: (i) sufficiently large sin θ/λ range of >0.8 Å−1; (ii) adequate counting statistics; (iii) correct profile model; (iv) proper weighting on observations to give a uniform distribution of the mean weighted squared residuals; (v) high-angular-resolution powder diffraction data.

Modulation of atomic positions in CaCu x Mn7−x O12 (x ≤ 0.1)

2009 ◽  
Vol 65 (5) ◽  
pp. 535-542 ◽  
Author(s):  
W. Sławiński ◽  
R. Przeniosło ◽  
I. Sosnowska ◽  
M. Bieringer ◽  
I. Margiolaki ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Low Temperature ◽  
Long Range ◽  
Powder Diffraction ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Neutron Powder Diffraction

The modulation of atomic positions in CaCu x Mn7−x O12 (x = 0 and 0.1) was studied using synchrotron radiation powder diffraction below 250 and 220 K, respectively. The copper-rich member CaCu x Mn7−x O12 (x = 0.23) does not show any modulation of the atomic positions at temperatures as low as 10 K. Using low-temperature neutron powder diffraction the modulation of the magnetic moments of Mn ions in CaCu x Mn7−x O12 (x = 0, 0.1 and 0.23) has been investigated. Long-range modulated magnetic ordering in CaCu x Mn7−x O12 (x = 0, 0.1 and 0.23) is observed below 90.4, 89.2 and 78.1 K. (0,0,q p) and (0,0,q m) are the propagation vectors describing the modulations of the atomic positions and the magnetic moments. For CaCu x Mn7−x O12 (x = 0 and 0.1) the magnetic modulation and atomic modulation lengths are related by a factor of 2 satisfying the relation (1 − q p) = 2(1 − q m).

Coexistence of magnetic and atomic position modulations in CaMn7O12

2014 ◽  
Vol 70 (a1) ◽  
pp. C517-C517
Author(s):  
Radosław Przeniosło ◽  
Wojciech Sławiński ◽  
Dariusz Wardecki ◽  
Izabela Sosnowska ◽  
Lukas Keller ◽  
...  
Keyword(s):  
Magnetic Moments ◽  
Complex Structure ◽  
Experimental Studies ◽  
Magnetic Ordering ◽  
Electric Polarization ◽  
Orbital Ordering ◽  
Atomic Position ◽  
Spin Lattice ◽  
Fundamental Information ◽  
Very High

The rhombohedral CaMn7O12 manganite is an important material which shows magnetoelectrioc coupling with very high values of the electric polarization [1]. These outstanding properties motivated many experimental studies and also theoretical analysis. The mechanism which leads to these extraordinary properties has not been explained up to now. A fundamental information needed for such studies is the crystal structure and the magnetic ordering. CaMn7O12 has a complex structure with a magnetic moments modulation below TN=90K [1,2], a modulation of the atomic positions below TC=250K [2] and also orbital ordering. The magnetic modulation propagation vector qm is related with the atomic positions modulation vector qp by the relation qp=2qm [2]. This 2:1 relation is valid across a large range of temperatures and show the importance of spin-lattice coupling. The crystal and magnetic structure of CaMn7O12 was studied by neutron powder diffraction at the instrument DMC at SINQ [3]. The magnetic and atomic position modulations are described by using the superspace group formalism. This approach is especially important for description of both modulations with the same model [2]. The resulting magnetic ordering model obtained in [3] is more precise as compared with earlier works [1,2]. The present results [3] differ from those published by other authors [1]. The important difference is that in the present studies the angle, Phi, between Mn3+ and Mn4+ magnetic moments located in the same (001) planes (Phi = 0.99(2)Pi), i.e. the moments are antiparallel, whereas Johnson et al. [1] determined this angle as Phi=0.84(4) Pi. This angle is an important parameter of the model Hamiltonians describing the electronic and magnetic properties of CaMn7O12.

Comparative study of the field-induced and spontaneous AF2′ multiferroic phases in MnWO4 and Mn0.90Co0.10WO4 within the magnetic symmetry framework

2016 ◽  
Vol 49 (2) ◽  
pp. 520-527
Author(s):  
Irene Urcelay-Olabarria ◽  
José Luis García-Muñoz ◽  
Eric Ressouche ◽  
Alexander A. Mukhin ◽  
Vassil Skumryev
Keyword(s):  
Comparative Study ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Polarization Vector ◽  
Physical Conditions ◽  
Magnetic Orders ◽  
Magnetic Symmetry ◽  
Two Phases ◽  
The One ◽  
Modulation Vector

(Mn,Co)WO4 compounds are regarded as reference spin-induced multiferroics. A comparative study is presented here, within the magnetic symmetry framework, of the incommensurate magnetic orders responsible for the ferroelectric phases of (i) MnWO4 under a magnetic field (H || b) and (ii) Mn0.90Co0.10WO4 in the absence of an external field. On the one hand, although these two ferroelectric phases are stabilized under different external physical conditions, both present the same Xc1′(α0γ)ss magnetic symmetry and practically the same modulation vector. The magnetic ordering in both phases is an elliptical helix with the magnetic moments (as the polarization vector, P) perpendicular to the b axis, although in most of the ferroelectric compositions of the (Mn,Co)WO4 family the spins rotate in planes containing b (and have P || b). On the other hand, the anisotropy of the resulting magnetic modulations is extraordinarily different in the two phases. This is described and explained in the light of the different anisotropies of Co and Mn ions.

The crystal structure of La0.7Pr0.3Ba2Cu3Od ceramic compound

2002 ◽  
Vol 17 (1) ◽  
pp. 25-29 ◽  
Author(s):  
X. S. Wu ◽  
H. Sha ◽  
W. S. Tan ◽  
Tao Yu ◽  
A. Hu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Synchrotron Radiation ◽  
Room Temperature ◽  
Total Content ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Orthorhombic System ◽  
X Ray ◽  
Ceramic Compound ◽  
Content Of Oxygen

The structure of new La0.7Pr0.3Ba2Cu3Oy (LPBCO) compound was obtained at room temperature from synchrotron radiation X-ray powder diffraction data and refined by Rietveld technique. LPBCO has an isotypical structure with YBa2Cu3Oy (YBCO). The crystal data are: La0.7Pr0.3Ba2Cu3O6.96, Mr=716.16, orthorhombic system, space group Pmmm, a=3.9147(1) Å, b=3.8672(1) Å, c=11.7033(2) Å, V=177.177(6) Å3, Z=1, Dx=6.714 g/cm3; the structure was refined with 35 parameters to Rwp=7.41%, Rp=5.32%, and Rexp=3.07% for 5001 step intensities. Moreover, the total content of oxygen in a unit cell is refined as 6.96, which is less than that of the calculated one. We attribute the superconductivity-depression to the increase of the valence of copper.

Crystal structure of donepezil hydrochloride form III, C24H29NO3⋅HCl

2021 ◽  
pp. 1-8
Author(s):  
Joel W. Reid ◽  
James A. Kaduk
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Powder Diffraction ◽  
Density Functional ◽  
Chloride Anion ◽  
Powder Diffraction Data ◽  
Powder Diffraction File ◽  
Functional Theory ◽  
Monoclinic Lattice ◽  
Donepezil Hydrochloride

The crystal structure of donepezil hydrochloride, form III, has been solved with FOX using laboratory powder diffraction data previously submitted to and published in the Powder Diffraction File. Rietveld refinement with GSAS yielded monoclinic lattice parameters of a = 14.3662(9) Å, b = 11.8384(6) Å, c = 13.5572(7) Å, and β = 107.7560(26)° (C24H30ClNO3, Z = 4, space group P21/c). The Rietveld-refined structure was compared to a density functional theory (DFT)-optimized structure, and the structures exhibit excellent agreement. Layers of donepezil molecules parallel to the (101) planes are maintained by columns of chloride anions along the b-axis, where each chloride anion hydrogen bonds to three donepezil molecules each.

scholarly journals Revealing noncollinear magnetic ordering at the atomic scale via XMCD

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fridtjof Kielgast ◽  
Ivan Baev ◽  
Torben Beeck ◽  
Federico Pressacco ◽  
Michael Martins
Keyword(s):  
Ground State ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Atomic Scale ◽  
Angle Of Incidence ◽  
X Ray ◽  
First Time ◽  
X Ray Absorption ◽  
Magnetic Sublattices

AbstractMass-selected V and Fe monomers, as well as the heterodimer $${\text{Fe}}_1{\text{V}}_1$$ Fe 1 V 1 , were deposited on a Cu(001) surface. Their electronic and magnetic properties were investigated via X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopy. Anisotropies in the magnetic moments of the deposited species could be examined by means of angle resolving XMCD, i.e. changing the X-ray angle of incidence. A weak adatom-substrate-coupling was found for both elements and, using group theoretical arguments, the ground state symmetries of the adatoms were determined. For the dimer, a switching from antiparallel to parallel orientation of the respective magnetic moments was observed. We show that this is due to the existence of a noncollinear spin-flop phase in the deposited dimers, which could be observed for the first time in such a small system. Making use of the two magnetic sublattices model, we were able to find the relative orientations for the dimer magnetic moments for different incidence angles.

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