Spin Magnetic Form Factors Research Articles

A study of magnetic moments of CeRh3B2 by X-ray magnetic diffraction experiments

X-ray magnetic diffraction experiments of a ferromagnetic rare-earth compound CeRh3B2 have been performed, and the spin and orbital magnetic form factors have been measured. Density distributions of the spin and orbital magnetic moments in real space have been obtained by using Maximum Entropy Method. Low peaks at Rh sites as well as high peaks at Ce sites are observed in these distribution maps. We have estimated the spin and orbital magnetic moments at the Ce and Rh sites in the distribution maps, and have obtained small but nonnegligible spin and orbital magnetic moments of Rh. This is probably the first experimental evidence showing existence of the spin and orbital moments of Rh in this compound.

X-Ray Magnetic Diffraction Experiment of Fe<sub>3</sub>Pt Alloy in Order Phase

We have performed X-ray magnetic diffraction experiments of a ferromagnetic binary alloy Fe3Pt in order phase, and have measured separately spin and orbital magnetic form factors. By a curve-fitting analysis in which atomic-model form factors of Fe-3d and Pt-5d electrons under the dipole approximation are assumed, we have obtained the spin and orbital magnetic moments of Fe and Pt atoms separately. The present result is comparable to those of other experimental and theoretical studies, which shows the validity of this experimental method.

A Study of Spin and Orbital Magnetic Form Factors of CeRh<sub>3</sub>B<sub>2 </sub> by X-Ray Magnetic Diffraction

An experimental method of X-ray magnetic diffraction was applied to the ferromagnetic rare-earth compound CeRh3B2, and its spin and orbital magnetic form factors were measured independently for the first time. Our curve-fitting analysis shows that the orbital magnetic form factor is reproduced by the calculated atomic-model form factor of Ce-4f electrons under the dipole approximation. The comparison of the sum of form factors and the total magnetic form factor measured by the polarized neutron diffraction reveals anisotropic distribution of the magnetic moment in real space.

Application of Upgraded X-ray Magnetic Diffraction Experimental System to 3d- and 4f-Electron Ferromagnets

An experimental system of X-ray magnetic diffraction (XMD) is developed on BL3C at the Photon Factory (PF) of High Energy Research Organization (KEK). We applied this upgraded XMD experimental system to 3d- and 4f-electron ferromagnet, YTiO3 and CeRh3B2, respectively. In YTiO3 we successfully obtained spin magnetic form factor for 31 reciprocal lattice points. The observed spin magnetic form factor suggests anisotropic spin density distribution in real space. In CeRh3B2 we succeeded in measuring spin and orbital magnetic form factor separately. We found that the dominant part of the magnetic moment is the orbital component in CeRh3B2. [DOI: 10.1380/ejssnt.2011.134]

Spin and Orbital Magnetic Moment of Pd<sub>3</sub>Co Evaluated by X-Ray Magnetic Diffraction Experiment

We have measured spin and orbital magnetic form factors of Pd3Co for various reciprocal lattice points by the X-ray magnetic diffraction. Observed spin and orbital magnetic form factors are fitted by theoretical curves of the isolated atomic model under the dipole approximation. By the fitting analysis we have evaluated separately the spin and orbital component of the magnetic moment of Pd3Co alloy as 2.19 µB/f.u. and 0.83 µB/f.u., respectively. The total magnetic moment 3.02 µB/f.u. is comparable to the value of 2.93 µB/f.u. obtained by the magnetization measurement.

Spin Density Distribution of YTiO<sub>3</sub> Observed by X-Ray Magnetic Diffraction

An X-ray magnetic diffraction (XMD) is applied to ferromagnetic transition metal oxide YTiO3. The spin magnetic form factors are measured for 81 reciprocal lattice points of h0l, hk0 and 0kl series. Three-dimensional spin density distribution in the real space of YTiO3 is successfully obtained by using Maximum Entropy Method (MEM). This is the first result of spin density in the real space by the XMD.

An Experimental System of X-ray Magnetic Diffraction at the Photon Factory

An experimental system of X-ray magnetic diffraction (XMD) for ferromagents is established at the Photon Factory in KEK to realize high photon-counting rate up to 105 cps and high magnetic-field strength over 20 kOe. These performances have been achieved by upgrading (i) an X-ray detector and photon-counting apparatus and (ii) an electromagnet, respectively. The spin magnetic form factor of ferromagnetic YTiO3 for 30 reciprocal lattice points of hk0 and 0kl series has been measured by using the XMD system in various geometries including magnetic-field direction parallel to the hard axis. The result is in good agreement with that of the neutron diffraction experiment. This fact shows that the system is valuable for measuring magnetic form factor of ferromagnets. In this paper we report the details of the system.

Study of spin and orbital magnetic form factors of CeRh3B2by X-ray magnetic diffraction

Study of spin and orbital magnetic form factors of CeRh₃B₂by X-ray magnetic diffraction

Direct observation of ordered orbital of YTiO3 by the X-ray magnetic diffraction technique

X-ray magnetic diffraction (XMD) technique was applied to an orbital ordering compound of ferromagnetic YTiO3 for the first time. The orbital-magnetic form factor μL(k) and the spin-magnetic form factor μS(k) were independently measured by utilizing the LS separation ability of the XMD. The μL(k) was measured for ten reciprocal-lattice points. No significant values of the μL(k) were observed for most of the reciprocal-lattice points within the estimated statistical errors, which suggested quenching of the orbital moment. The μS(k) was measured for 22 reciprocal-lattice points. Fourier synthesis of the μS(k) gave the spin density distribution mS(r) in the real space. The obtained mS(r) map shows the characteristic feature of the electron distribution of 3d electron in the t2g state of a Ti atom coordinated by O2− ions, in which the electrons are distributed away from the negative O2− ions. It is concluded that the electron distribution of the 3d electron of the Ti atom, that is, the ordered orbital (or the wave function) of YTiO3 was observed in the real space by the XMD technique.

Observation of ordered orbital of YTIO 3 by the X-ray magnetic diffraction experiments

X-ray magnetic diffraction (XMD) experiments of ferromagnetic YTiO 3 were performed. The orbital-magnetic form factor (L) and the spin-magnetic form factor (S) were individually measured by utilizing the LS separation method of the XMD. The experiments consisted of two parts. The first was the measurement of the orbital-magnetic form factor to examine whether the orbital moment of this compound was quenched or not. The second was the measurement of the spin-magnetic form factor to examine whether the ordered orbital of Ti-3d electrons was observed by the XMD. The result of the first experiment suggested quenching of the orbital moment. In the second experiment, the spin-magnetic form factor was observed for the total 22 reciprocal-lattice points. Calculated spin-magnetic form factor with a model wave function of the ordered orbital reproduced the observed one well. This result shows that the ordered orbital of Ti-3d electrons can be observed by the XMD.

放射光Ｘ線による磁気回折の研究 偏光と磁気と回折

X-ray magnetic diffraction experiment of ferromagnets that utilizes elliptically polarized synchrotron radiation is presented. First we have reviewed shortly historical backgrounds and theoretical aspects of the experiment. We have presented how the magnetic form factors are measured and are separated into the spin-moment component and the orbital-moment component in this experiment. Peculiar features of the polarization factor of this experiment have been explained. We have introduced two examples of the experiment. One is the measurement of the spin-magnetic form factor of SmAl2 with white X-rays from a bending magnet at the Photon Factory. The other is the measurement of the orbital-magnetic form factor of Holmium Iron Garnets with monochromatic X-rays from an undulator at the SPring-8. Finally we summarize the article and show some future prospects of this experiment.

Spin Magnetic Form Factors of hcp Co

Spin magnetic form factors of hcp cobalt are calculated by the APW method using the SDF potential. The results are compared with the experimental values obtained by neutron diffraction and recent white beam method of x-ray magnetic diffraction.

ORBITAL PARAMAGNETISM IN METALLIC SYSTEMS WITH LARGE ANGULAR MOMENTA

We demonstrate that the field induced spin and orbital moments in paramagnetic metals in general are parallel, since the Zeeman energy overcomes the spin-orbit energy that is in favor of an antiparallel arrangement when the electronic shell is less than half-filled. In the early actinides, however, the spin-orbit energy becomes sufficiently strong to approach the border where the moments can couple antiparallel. This results in peculiar magnetic states for α-Pu and some uranium compounds, where the spin moments are antiparallel to the applied field and the magnetic response dominated by the orbital character, and consequently these systems display unusual spin densities and magnetic form factors.

Field-induced magnetism in actinide systems

We demonstrate that the field-induced spin and orbital moments in paramagnetic metals in general are parallel, regardless of the filling of the electronic shell. The early actinides, however, approach the border where the moments go antiparallel. This results in peculiar magnetic states for α-Pu and some uranium compounds, where the spin moments are antiparallel to the applied field and the magnetic response is dominated by the orbital contribution, and consequently these systems display unusual spin densities and magnetic form factors.

Spin magnetic form factors for lithium and its isoelectronic series in position and momentum space

For the lithium atom, spherically averaged total and magnetic form factors, F(k) and M(k), and internally folded densities, B(s) and Q(s) have been calculated from highly accurate configuration interaction wavefunctions. Their general functional behaviour is analysed together with those from the lithium isoelectronic series (Be+ to Ne7+). The influence of electron correlation on these properties is investigated by comparisons with calculations obtained from Hartree-Fock wavefunctions.

A relativistic spin-polarised band theoretical study of magnetic properties of nickel and iron

In order to study the relativistic effects on the magnetic properties of transition metals, we have performed self-consistent relativistic spin-polarised electronic band structure calculations for two cubic systems: Ni and Fe. The spin-polarised fully relativistic linear muffin-tin orbital method is used. The calculated ground state spin and orbital magnetic moments and magnetic form factors for Ni and Fe are presented. The magneto-crystalline anisotropy in the band structure is studied, by rotating the magnetisation direction from (0 0 1) to (1 1 1) and then to (1 1 0). Finally, a computationally very intensive study of the magneto-crystalline anisotropy energy and moment has been carried out.

Spin magnetic form factors for cobalt and nickel: including atomic correlation and LS-dependent relativistic effects

Spin magnetic form factors for the first-row transition-metal atoms cobalt and nickel have been evaluated using non-relativistic and 'relativistic-corrected' configuration interaction wavefunctions of varying accuracy in the mod LSMLMS) representation. Relaxing the constraints imposed by the Hartree-Fock model results in a small expansion of the spin magnetic form factors in reciprocal space, corresponding to a small contraction of the spin-density distribution in real space. Including the LS-dependent relativistic effects in the Breit-Pauli approximation results in a further expansion of the spin magnetic form factors in reciprocal space, corresponding to a greater contraction of the spin-density distribution in real space.

Spin magnetic form factors for doubly charged ions in the first transition-metal series

Spin magnetic form factors for the ground states of the doubly charged cobalt and nickel ions have been evaluated using non-relativistic and 'relativistic-corrected' configuration interaction wavefunctions of varying accuracy in the mod LSMLMS) representation. The importance of incorporating all types of electron correlation systematically within the 3d shell while keeping a fixed argon core is discussed. From the results presented it would appear that, at the present level of accuracy of experimental measurement, the restricted Hartree-Fock free-ion spin magnetic form factors corresponding to the Fourier transform of the scattering density are of sufficient accuracy for the analysis of the spin-density distribution in transition-metal-atom complexes.

Induced neutron magnetic form factor of LaSn 3

Polarized neutron scattering techniques have been used to study the spatial distribution of the magnetization induced in a single crystal of LaSn 3 by a magnetic field of 42.5 kG at 100 K. We find that the magnetic form factor decreases very rapidly with increasing scattering angle, and bears no resemblance to the spin or orbital free-atom magnetic form factor. The experimental results are in reasonable agreement with band theoretical calculations of the spin magnetic form factor of LaSn 3. We conclude that (a) the spin part is the dominant contribution to the bulk susceptibility of LaSn 3 and (b) there is a substantial amount of Sn-5p electronic character in the wavefunctions near the Fermi level.

Field-induced magnetic form factor of lutetium

The conduction electron field-induced magnetic form factor of Lu, a rare earth metal with a closed 4f shell, has been measured using the polarized neutron technique. The measurements demonstrate that the conduction electron density is more spatially extended than in the free atom. The experimental results are in good agreement with band calculations of the spin magnetic form factor.