scholarly journals Quantifying magnetic anisotropy using X-ray and neutron diffraction

IUCrJ ◽  
2021 ◽  
Vol 8 (5) ◽  
Author(s):  
Emil Andreasen Klahn ◽  
Emil Damgaard-Møller ◽  
Lennard Krause ◽  
Iurii Kibalin ◽  
Arsen Gukasov ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Magnetic Anisotropy ◽  
Ab Initio ◽  
Single Molecule ◽  
Ligand Field ◽  
Zero Field ◽  
X Ray Diffraction ◽  
Zero Field Splitting ◽  
X Ray

In this work, the magnetic anisotropy in two iso-structural distorted tetrahedral Co(II) complexes, CoX 2tmtu2 [X = Cl(1) and Br(2), tmtu = tetramethylthiourea] is investigated, using a combination of polarized neutron diffraction (PND), very low-temperature high-resolution synchrotron X-ray diffraction and CASSCF/NEVPT2 ab initio calculations. Here, it was found consistently among all methods that the compounds have an easy axis of magnetization pointing nearly along the bisector of the compression angle, with minute deviations between PND and theory. Importantly, this work represents the first derivation of the atomic susceptibility tensor based on powder PND for a single-molecule magnet and the comparison thereof with ab initio calculations and high-resolution X-ray diffraction. Theoretical ab initio ligand field theory (AILFT) analysis finds the d xy orbital to be stabilized relative to the d xz and d yz orbitals, thus providing the intuitive explanation for the presence of a negative zero-field splitting parameter, D, from coupling and thus mixing of d xy and d x 2  −  y 2 . Experimental d-orbital populations support this interpretation, showing in addition that the metal–ligand covalency is larger for Br-ligated 2 than for Cl-ligated 1.

Investigation of Residual Strains of the Second Kind in Plastically Deformed Metallic Materials

1994 ◽  
Vol 376 ◽  
Author(s):  
M. Vrána ◽  
P. Klimanek ◽  
T. Kschidock ◽  
P. Lukáš ◽  
P. Mikula
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Stacking Faults ◽  
Metallic Materials ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutron Diffractometer ◽  
Residual Strains ◽  
Good Agreement

ABSTRACTInvestigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.

scholarly journals High-resolution ab initio three-dimensional x-ray diffraction microscopy

2006 ◽  
Vol 23 (5) ◽  
pp. 1179 ◽  
Author(s):  
Henry N. Chapman ◽  
Anton Barty ◽  
Stefano Marchesini ◽  
Aleksandr Noy ◽  
Stefan P. Hau-Riege ◽  
...  
Keyword(s):  
High Resolution ◽  
Ab Initio ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Microscopy

The whole range of hydrogen bonds in one crystal structure: neutron diffraction and charge-density studies of N,N-dimethylbiguanidinium bis(hydrogensquarate)

2011 ◽  
Vol 67 (6) ◽  
pp. 552-559 ◽  
Author(s):  
Mihaela-Diana Şerb ◽  
Ruimin Wang ◽  
Martin Meven ◽  
Ulli Englert
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
High Resolution ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Electron Density ◽  
Organic Salt ◽  
X Ray Diffraction ◽  
Covalent Character ◽  
X Ray

N,N-Dimethylbiguanidinium bis(hydrogensquarate) features an impressive range of hydrogen bonds within the same crystal structure: neighbouring anions aggregate to a dianionic pair through two strong O—H...O interactions; one of these can be classified among the shortest hydrogen bonds ever studied. Cations and anions in this organic salt further interact via conventional N—H...O and nonclassical C—H...O contacts to an extended structure. As all these interactions occur in the same sample, the title compound is particularly suitable to monitor even subtle trends in hydrogen bonds. Neutron and high-resolution X-ray diffraction experiments have enabled us to determine the electron density precisely and to address its properties with an emphasis on the nature of the X—H...O interactions. Sensitive criteria such as the Laplacian of the electron density and energy densities in the bond-critical points reveal the incipient covalent character of the shortest O—H...O bond. These findings are in agreement with the precise geometry from neutron diffraction: the shortest hydrogen bond is also significantly more symmetric than the longer interactions.

High-Resolution X-ray Diffraction and ab Initio Quantum Chemical Studies of Glycoluril, a Biotin Analog

1994 ◽  
Vol 116 (15) ◽  
pp. 6494-6507 ◽  
Author(s):  
Naiyin Li ◽  
Sergio Maluendes ◽  
Robert H. Blessing ◽  
Michel Dupuis ◽  
Grant R. Moss ◽  
...  
Keyword(s):  
High Resolution ◽  
Ab Initio ◽  
Quantum Chemical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chemical Studies ◽  
Quantum Chemical Studies

scholarly journals Neutron diffraction and ab initio studies on the fully compensated ferrimagnetic characteristics of Mn2V1-xCoxGa Heusler alloys

2021 ◽  
Author(s):  
Midhunlal P V ◽  
Venkatesh Chandragiri ◽  
J Arout Chelvane ◽  
P D Babu ◽  
Harish Kumar Narayanan
Keyword(s):  
Neutron Diffraction ◽  
Ab Initio ◽  
Structural Transition ◽  
Magnetic Measurements ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atom Pairs ◽  
Co Concentration

Abstract Neutron diffraction and ab initio studies were carried out on Mn2V1-xCoxGa (x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys which exhibits high TC fully compensated ferrimagnetic characteristics for x = 0.5. A combined analysis of neutron diffraction and ab initio calculations revealed the crystal structure and magnetic configuration which could not be determined from the X-ray diffraction and magnetic measurements. As reported earlier, Rietveld refinement of neutron diffraction data confirmed L21 structure for Mn2VGa and Xa structure for Mn2CoGa. The alloys with x = 0.25 and 0.5 possess L21 structure with Mn(C)-Co disorder. As the Co concentration reaches 0.75, a structural transition has been observed from disordered L21 to disordered X a. Detailed ab initio studies also confirmed this structural transition. The reason for the magnetic moment compensation in Mn2(V1-xCox)Ga was identified to be different from that of the earlier reported fully compensated ferrimagnet (MnCo)VGa. With the help of neutron diffraction and ab initio studies, it is identified that the disordered L21 structure with antiparallel coupling between the ferromagnetically aligned magnetic moments of (Mn(A)-Mn(C)) and (V-Co) atom pairs enables the compensation in Mn2V1-xCoxGa.

scholarly journals Is [ReCl4(CN)2]2− a good Building Block for Single Molecule Magnets? A Theoretical Investigation.

2022 ◽  
Author(s):  
Christoph van Wüllen ◽  
Eva M. V. Kessler
Keyword(s):  
Single Molecule ◽  
Building Blocks ◽  
Ligand Field ◽  
Zero Field ◽  
Spin Orbit ◽  
Computational Results ◽  
Zero Field Splitting ◽  
Single Molecule Magnets ◽  
Field Splitting ◽  
Orbit Perturbation

Building blocks containing $5d$ spin centres are promising for constructing single molecule magnets due to their large spin-orbit interaction, but experimental and computational results obtained so far indicate that this might not be the case for Re$^\textrm{IV}$ centres in an octahedral environment. Density functional results obtained in this work for [ReCl$_4$(CN)$_2$]$^{2-}$ and trinuclear complexes formed by attaching Mn$^\textrm{II}$ centres to the cyano ligands indicate that zero field splitting in such complexes exhibits large rhombicity (which leads to fast relaxation of the magnetisation) even if there are only small distortions from an ideal geometry with a four-fold symmetry axis. This is already apparent if second-order spin-orbit perturbation theory is applied but even more pronounced if higher-order spin-orbit effects are included as well, as demonstrated by wavefunction based calculations. Computational results are cast into a ligand field model and these simulations show that especially a distortion which is not along the $C_4/C_2$ axeshas a large effect on the rhombicity. Quantum simulations on these complexes are difficult because the zero field splitting strongly depends on the energetic position of the low-lying doublets from the $t_{2g}^3$ configuration.

scholarly journals EMR-related problems at the interface between the crystal field Hamiltonians and the zero-field splitting Hamiltonians

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 377-383
Author(s):  
Czesław Rudowicz ◽  
Mirosław Karbowiak
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Anisotropy ◽  
Crystal Field ◽  
Recent Literature ◽  
Ligand Field ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Effective Spin ◽  
Spin Hamiltonians

Abstract The interface between optical spectroscopy, electron magnetic resonance (EMR), and magnetism of transition ions forms the intricate web of interrelated notions. Major notions are the physical Hamiltonians, which include the crystal field (CF) (or equivalently ligand field (LF)) Hamiltonians, and the effective spin Hamiltonians (SH), which include the zero-field splitting (ZFS) Hamiltonians as well as to a certain extent also the notion of magnetic anisotropy (MA). Survey of recent literature has revealed that this interface, denoted CF (LF) ↔ SH (ZFS), has become dangerously entangled over the years. The same notion is referred to by three names that are not synonymous: CF (LF), SH (ZFS), and MA. In view of the strong need for systematization of nomenclature aimed at bringing order to the multitude of different Hamiltonians and the associated quantities, we have embarked on this systematization. In this article, we do an overview of our efforts aimed at providing a deeper understanding of the major intricacies occurring at the CF (LF) ↔ SH (ZFS) interface with the focus on the EMR-related problems for transition ions.

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