scholarly journals Sixty Five Years of Magnetic Structures. Present and Future of Magnetic Crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C24-C24
Author(s):  
Juan Rodriguez-Carvajal
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moments ◽  
Spatial Arrangement ◽  
Physical Review ◽  
Three Dimensions ◽  
Magnetic Structures ◽  
Symmetry Properties ◽  
Special Cases

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 neutron diffraction (powder and single crystals) and in special cases the use of polarized neutrons is necessary to solve ambiguities found in the interpretation of magnetic neutron diffraction data. We can consider that Magnetic Crystallography starts with the seminal paper by C.G. Shull and S. Smart on the magnetic structure of MnO published the 29 August 1949 in the Physical Review 76, 1256. The symmetry properties of periodic arrangement of atoms are well described by the 230 space group types in three dimensions, however more complex spatial arrangements of atoms may need to be described by periodicity in higher dimensions. Incommensurate, composite and quasi-crystal structures represent a relatively small part of the huge amount of materials that can be described by conventional Crystallography, however many magnetic structures are non-commensurate: the periodicity of the orientation of the magnetic moments is not commensurate with the underlying crystal structure. The symmetry properties of magnetic structures are traditionally described using two different approaches: the magnetic Shubnikov groups [1] and the group representation analysis [2-3]. In this talk we shall describe how these approaches have been established historically and the advantages of the new trend towards the use of magnetic superspace groups. A review of the most important papers and milestones in magnetic neutron scattering as well as in the symmetry concepts will be presented. The current analytical tools and methods for determining magnetic structures and their symmetry will briefly be described.

Magnetic Diffraction

2020 ◽  
pp. 213-256
Author(s):  
Andrew T. Boothroyd
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Phase Transitions ◽  
Magnetic Scattering ◽  
Neutron Polarization ◽  
Static Approximation ◽  
Spin Order ◽  
Magnetic Structures ◽  
Unit Cells

The basic concepts of magnetic order in crystals are reviewed, including magnetic unit cells, propagation vectors and magnetic domains. Some commonly-occuring magnetic structures are discussed, such as ferromagnets, antiferromagnets, ferrimagnets, and noncollinear and incommensurate magnetic structures. The differential cross-section for neutron diffraction from a magnetic structure is derived, and the magnetic structure factor is defined. The use of neutron polarization analysis, including spherical neutron polarimetry, in the determination of magnetic structures and of the spatial distribution of magnetization is described in detail. Diffuse magnetic scattering due to magnetic frustration and magnetic phase transitions is discussed, and the relevance of the static approximation is explained. Neutron diffraction studies of nuclear spin order are described.

scholarly journals Crystal and magnetic structures of R 2Ni1.78In compounds (R = Tb, Ho, Er and Tm)

2021 ◽  
Vol 77 (5) ◽  
pp. 824-832
Author(s):  
Stanisław Baran ◽  
Aleksandra Deptuch ◽  
Andreas Hoser ◽  
Bogusław Penc ◽  
Yuriy Tyvanchuk ◽  
...  
Keyword(s):  
Rare Earth ◽  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moments ◽  
Symmetry Analysis ◽  
Crystalline Electric Field ◽  
Magnetic Structures ◽  
Antiferromagnetic Ordering ◽  
Crystal And Magnetic Structures ◽  
The Rare Earth

The crystal and magnetic structures in R 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx , kx , ½], with kx equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.

Magnetic Structure Determination of CeT2Al10 (T = Ru and Os): Single Crystal Neutron Diffraction Studies

2011 ◽  
Vol 80 (7) ◽  
pp. 073701 ◽  
Author(s):  
Harukazu Kato ◽  
Riki Kobayashi ◽  
Tomoaki Takesaka ◽  
Takashi Nishioka ◽  
Masahiro Matsumura ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Magnetic Structure ◽  
Structure Determination

Magnetic Structure of Manganese Pyrophosphate and Copper Pyrophosphate

1972 ◽  
Vol 50 (24) ◽  
pp. 3079-3084 ◽  
Author(s):  
J. A. R. Stiles ◽  
C. V. Stager
Keyword(s):  
Phase Transition ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Magnetic Structure ◽  
Magnetic Structures

The magnetic structures of antiferromagnetic manganese pyrophosphate and copper pyrophosphate have been determined by single crystal neutron diffraction techniques. There have been two previous determinations of the structure of manganese pyrophosphate. The discrepancy between these results is explained by postulating a crystallographic phase transition.

Strukturen cäsiumhaltiger Fluoride, II1 Die Kristall- und Magnetische Struktur von CsFeF4 / Crystal and Magnetic Structure of CsFeF4

1974 ◽  
Vol 29 (3-4) ◽  
pp. 139-148 ◽  
Author(s):  
D. Babel ◽  
F. Wall ◽  
G. Heger
Keyword(s):  
Neutron Diffraction ◽  
Single Crystals ◽  
Magnetic Structure ◽  
Structure Determination ◽  
Mean Value ◽  
X Ray ◽  
Magnetic Structures ◽  
Powder Samples ◽  
Crystal And Magnetic Structure ◽  
Improved Model

The results of an X-ray structure determination on single crystals of CsFeF4 are reported. The compound crystallizes tetragonally with α = 7.794, c = 6.553 Å, z = 4, in spacegroup P4/nmm-D4h7 and is a hitherto unknown superstructure variant of the TlAlF4-type. Cesium exhibits 12-coordination (mean value Cs-F = 3.25 Å); the FeF6-octahedra are characteristically shortened normal to the FeF4⁻-layers (Fe-F = 1.962/1.861Å). An improved model is proposed and verified for a related structure of RbFeF4, showing the same features. Neutron diffraction studies on powder samples of CsFeF4 show that both compounds are identical as for their magnetic structures.

Complex magnetic ordering inNdNi1−xCux: Determination of the magnetic structure by neutron diffraction

2004 ◽  
Vol 70 (22) ◽  
Author(s):  
J. García Soldevilla ◽  
J. A. Blanco ◽  
J. Rodríguez Fernández ◽  
J. I. Espeso ◽  
J. C. Gómez Sal ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Ordering

Magnetic structure determination of NdNiC2 and TmNiC2 by neutron diffraction

1990 ◽  
Vol 89 (3) ◽  
pp. 299-303 ◽  
Author(s):  
J.K. Yakinthos ◽  
P.A. Kotsanidis ◽  
W. Schäfer ◽  
G. Will
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Structure Determination

scholarly journals Magnetic structure analysis of rare earth permanent magnet Sm2Fe17N3

2014 ◽  
Vol 70 (a1) ◽  
pp. C1460-C1460 ◽  
Author(s):  
Kotaro Saito ◽  
Nobuhito Inami ◽  
Yasuo Takeichi ◽  
Tetsuro Ueno ◽  
Ryoko Sagayama ◽  
...  
Keyword(s):  
Rare Earth ◽  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Structure Analysis ◽  
Permanent Magnets ◽  
Nearest Neighbor ◽  
Magnetic Moments ◽  
High Coercivity ◽  
Diffraction Measurement ◽  
Fe Sites

Rare earth intermetallic compound Sm2Fe17N3 exhibits notalble magnetic properties such as high Curie temperature and high coercivity which are very suitable for permanent magnets [1,2]. Although microscopic magnetic structure is one of the basic information for magnetic materials, there is no report about the magnetic structure of Sm2Fe17N3 for our knowledge. This is because samarium's neutron absorption cross section is huge enough to make researchers hesitate to have neutron diffraction experiments of Sm compounds. We have carried out powder neutron diffraction measurement of Sm2Fe17N3 with a straightforward solution to the problem by taking long measurement time. Synchrotron x-ray diffraction measurements with single crystal has also been done to obtain initial crystal structure parameters for magnetic structure analysis and we have succeeded to analyze the magnetic structure of Sm2Fe17N3 at room temperature. Among four Fe sites in the unit cell, while one Fe site which is the nearest neighbor of nitrogen shows smaller magnetic moment than normal iron, two Fe sites show enhancement in their magnetic moments. This phenomenon can be understood as 'cobaltization' of Fe by the adjacent nitrogen through hybridization.

scholarly journals Determination of the crystal and magnetic structure of the DyCrO4-scheelite polymorph by neutron diffraction

2014 ◽  
Vol 549 ◽  
pp. 012021 ◽  
Author(s):  
A J Dos santos-García ◽  
E Climent-Pascual ◽  
M G Rabie ◽  
J Romero de Paz ◽  
J M Gallardo Amores ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Crystal And Magnetic Structure
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