Magnetic Compton Scattering Research Articles

Bayesian Orbital Decomposition and Determination of End Condition for Magnetic Compton Scattering

In this paper, we have demonstrated the orbital component decomposition for the magnetic Compton scattering spectrum of Fe poly crystal by using Bayesian inference and the non-relativistic Hartree–...

Magnetic Compton Scattering on Sr-Doped LaCoO3

We carried out magnetic Compton scattering experiments on the Sr-doped perovskite cobaltite La1−xSrxCoO3 for the paramagnetic insulator (x = 0.1) and the ferromagnetic metallic (x = 0.3) phases in order to investigate the electron-orbital state relevant to its unusual magnetic and electronic transport properties. The ratio of the orbital moments to the spin moments (Morbital/Mspin) is less than 1/10 at low temperatures for x = 0.3, whereas Morbital/Mspin is about 0.4 almost independent of temperature for x = 0.1. The shape of Jmag(pz) shows no apparent difference between the paramagnetic insulator and the ferromagnetic metallic phases.

Estimation of Angular Momentum Compensation Temperature in GdFe Film by Magnetic Compton Scattering

Estimation of Angular Momentum Compensation Temperature in GdFe Film by Magnetic Compton Scattering

Measurements of the Spin-Selective Magnetic Hysteresis Curve in Fe–3 wt.% Si Alloy Using Magnetic Compton Scattering

In order to resolve the total magnetization of Fe–3 wt.% Si into spin and orbital contributions, we attempted to measure the spin-selective magnetic hysteresis curve using magnetic Compton scattering. The spin-selective magnetic hysteresis curve as a function of an applied magnetic field was determined by analyzing the integrated intensity of magnetic Compton spectra, which reflect only the momentum density of spin-polarized electrons in Fe–3 wt.% Si alloy. The orbital magnetic hysteresis curve was obtained by taking the difference between the vibrating sample magnetometer loop and the spin-selective magnetic hysteresis curve. The results show that the spin moment dominates the total magnetization in Fe–3 wt.% Si alloy and the $$ g $$ value in the alloy is estimated to be 2.34, which is larger than that in a pure Fe metal, which is 2.09.

Magnetic Compton scattering study of grain-oriented silicon steels

Magnetic Compton profiles (MCPs) of grain-oriented silicon steels with different Si content were measured by a magnetic Compton scattering (MCS) technique. The profile features of the MCP difference between high permeability grain-oriented and conventional grain-oriented steels were similar to those of the theoretical sixth band related to the 3d conduction electrons of Fe. A comparison of the calculated eddy current losses between two samples revealed that Si content affects the contribution degree of 3d conduction electrons to eddy current losses. This brief note presents the relationship between electronic structure and eddy current loss.

Spin density in YTiO3 : II. Momentum-space representation of electron spin density supported by position-space results

Unpaired electrons in YTiO 3 ferromagnetic crystal (below 30 K) were studied by polarized neutron diffraction (PND) and incoherent x-ray magnetic Compton scattering (MCS). These experiments provide both position and momentum representations of the electrons at the origin of the magnetic behavior, mostly those in the t 2g state of Ti atoms. A two-dimensional reconstruction was conducted from experimental and theoretical directional magnetic Compton profiles to obtain the two-dimensional magnetic electron momentum density. A superposition method is proposed to examine the coherence between results for position and momentum spaces, respectively. This model-free approach allows a straightforward cross-checking of PND and MCS experiments. An isolated Ti model is proposed to emphasize the role played by O 1 in the ferromagnetic coupling between Ti and its neighboring atoms.

Magnetization and stability study of a cobalt-ferrite-based ferrofluid

In this study the structural and magnetization properties of a CoFe2O4-based ferrofluid was investigated using x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), Mössbauer spectroscopy, and magnetic Compton scattering (MCS) measurements. The XRD diagram indicates that the nanoparticles in the ferrofluid are inverse spinel and TEM graph shows that the ferrofluid consists of spherical nanoparticles with an average diameter of 18± 1nm, in good agreement with the size, 19.4nm, extracted from line broadening of the XRD peaks. According to EDS measurements the composition of the nanoparticles is CoFe2O4. Mössbauer spectroscopy shows that the cation distributions are (Co0.38Fe0.62)[Co0.62Fe1.38]O4. The MCS measurement, performed at 10K, indicates that the magnetization of the nanoparticles is similar to magnetization of maghemite and magnetite. While the magnetization of the inverse spinels are in [111] direction, interestingly, the magnetization deduced from MCS is in [100] direction. The CoFe2O4-based ferrofluid is found to be stable at ambient conditions, which is important for applications.

磁気コンプトン散乱で調べる化学結合の形とその磁場依存性～垂直磁化膜の起原～

磁気コンプトン散乱で調べる化学結合の形とその磁場依存性～垂直磁化膜の起原～

ChemInform Abstract: Magnetic Compton Scattering: A Reliable Probe to Investigate Magnetic Properties

AbstractReview: 8 refs.

Perpendicular Magnetic Anisotropy in Fe/MgO Multilayer Film Measured by Magnetic Compton Scattering

We have measured magnetic Compton scattering (MCS) for an Fe/MgO multilayer film at several magnetic field applying perpendicular to film plane. A spin specific magnetic hysteresis (SSMH) loop is obtained by the MCS for the Fe/MgO multilayer film. A knickpoint is observed in the SSMH loop around the magnetic field of 0.5 T. Orbital magnetization is enhanced within the magnetic field from-0.5 T to 0.5 T. A decomposition analysis for magnetic Compton profiles shows the suppressed |m|=0 states and enhanced |m|=1 and 2 states within the magnetic field from-0.5 T to 0.5 T. Heremdenotes magnetic quantum number. The knickpoint corresponds to a perpendicular magnetic anisotropy, which comes from the enhanced |m|=1 and 2 state and orbital magnetization in the Fe/MgO multilayer.

Feasibility of magnetic Compton scattering in measurement of small spin moments: A study on LaFe1−xNixO3 (x = 0.4 and 0.5)

Remarkable applicability of magnetic Compton scattering (MCS) in deducing site specific small spin moments like those in LaFe1−xNixO3 (x = 0.4 and 0.5) is established. The MCS measurements revealed that Fe site gives a dominant contribution (although small) to total magnetic moment, while the contribution of Ni spin moment is found to be antiparallel to that of Fe moment. Present work, which instigates insignificant role of orbital moment and diffused components in the formation of total magnetic moment, triggers era of applications of MCS in ferrimagnetic compounds with small magnetic moments.

Spin and orbital magnetization loops obtained using magnetic Compton scattering

We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl2 was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization.

Competition of 3d/4f orbitals due to competing conductivity and ferromagnetism in Fe/CoAs layers in Eu(Fe0.89Co0.11)2As2

The spin-polarized electron momentum density along the [100] direction of Eu(Fe0.89Co0.11)2As2 was measured using Magnetic Compton Scattering (MCS). Measurements were performed at different temperatures and applied external magnetic fields. These results provide the first direct insight into the orbital interactions that are responsible for the competing conductivity and ferromagnetism (FM) in this iron pnictide system. The orbital-wise decompositions of the density distribution show that at low applied magnetic field (0.1 T), the spin-polarized average Fe/Co-3d character is enhanced between 15 K and 19 K with a maximum at 17 K, the temperature at which the resistivity shows a local maximum, followed by re-entrant SC (superconducting)-like character. This clearly shows the dominance of the ferromagnetic character over conducting character in this temperature region where the resistivity shows a maximum. At higher applied magnetic field, we do not see this enhancement and subsequent collapse of the Fe/Co-3d character as the temperature decreases, consistent with the disappearance of the re-entrant SC-like feature at higher applied magnetic field. These data support a model in which the spin-polarization of the Fe/Co-3d orbitals is enhanced by the ferromagnetic Eu-ions, leading to the suppression of conductivity at ∼17 K (for 0.1 T), while at lower temperature the conductivity recovers and the Fe/Co-3d spin-polarization collapses.

Instability of Co Spin Moment in ErCo2 Probed by Magnetic Compton Scattering under High Pressure

Magnetic Compton scattering at high pressure is presented for the first time. To study the pressure-induced magnetic transition in Laves-phase ErCo 2 , Er 4 f and Co 3 d spin magnetic moments, together with the conduction electron component, were separately and quantitatively estimated at pressures up to 1.84 GPa. The Co 3 d spin moments show a remarkable reduction with increasing pressure, which is in contrast to the weak pressure variation of the Er 4 f spin moment. The relationship between the magnetic transition and instability of the Co 3 d moment at high pressure is discussed from the viewpoint of lattice contraction and the molecular field of Er 4 f moments.

Competing Ferromagnetism and Superconductivity on FeAs Layers inEuFe2(As0.73P0.27)2

We have measured the spin-polarized electron momentum density distributions of EuFe2(As0.73P0.27)2 by magnetic Compton scattering (MCS) measurements. For the first time, we show direct evidence of competing ferromagnetism and superconductivity (SC) on FeAs layers in this iron pnictide system. The MCS orbitalwise decomposition of the density distributions reveals that between 16 and 19 K, the spin-polarized Fe-3d character is enhanced (as the ferromagnetic character supersedes superconducting character), where the resistivity shows a maximum, reentrant SC-like peak, at 18 K. The spin polarization of the Fe-3d orbital, enhanced by ferromagnetic Eu ions, suppresses the SC around 18 K, while at other temperatures the system indeed exhibits SC where the Fe-3d spin polarization is suppressed or collapses.

Magnetic Compton Scattering Study of Shape Memory Alloys

The Compton profile, projection of electron momentum density distribution along the scattering vector, is very sensitive to the behavior of valence electrons in a variety of materials. In this paper theoretical aspects related to measurement of spin momentum densities of magnetic materials using Compton scattering is reviewed. To highlight the potential of the magnetic Compton scattering, the spin momentum densities in Ni-Mn-Ga Heusler alloys at various temperatures and magnetic fields are presented. The magnetic Compton profiles are mainly analyzed in terms of the contribution from the 3d electrons of Mn. A comparison of the magnetic Compton data with other magnetization studies illustrates its importance in exploring the magnetic effects in ferro- or ferri-magnetic materials.

Momentum–density distribution of magnetic electrons in ferromagnetic nickel

Experimental and theoretical investigations have been made for the first time on thethree-dimensional momentum–density distribution of magnetic electrons in ferromagnetic Ni,ρmag(p), which is the difference in the electron momentum–density distribution between majority- andminority-spin electrons. A magnetic Compton-scattering technique is used to determineρmag(p) by applying the direct Fourier-transform method to reconstructρmag(p) from magnetic Compton profiles. The corresponding theoreticalρmag(p) is calculated by the full-potential linearized augmented plane-wave method. Thepresent theory accurately reproduces the overall structures of experimentalρmag(p).There are, however, slight quantitative discrepancies between the experimental and calculated valuesof ρmag(p) around |p| = 0 au and at the positions related to the X-point. The analysis ofρmag(p) for individual bands attributes negativeρmag(p) near the first Brillouinzone boundary (|p|∼1.0 au) to the superposition of highly negative spin-polarized momentum–densityof the first band and highly positive spin-polarized momentum–densityof the sixth band. The positively polarized momentum–density at|p|∼2.2 au is attributed to the d-like fifth band spin polarizations.

Magnetic Compton Scattering Study on Metamagnetism in Itinerant Uranium Compounds

We have investigated the itinerant uranium compound UCoAl using the magnetic Compton scattering technique. We have measured magnetic Compton profiles at 5 K with an applied magnetic fields of 1 and 3 T, both above the metamagnetic transition. We found that the magnetic effect in magnetic Compton scattering is negative at 1 T, which demonstrates that the spin moments of uranium 5f electrons dominate the total spin moments in this compound. It is also observed that the absolute value of the magnetic effect decreases as the magnetic field increases. This suggests that the cobalt spin moment is induced or increased by increasing magnetic field.

Magnetic Compton Scattering Studies of Electrochemically Hydrogenated Nickel

The influence of hydrogen absorption on the electronic and magnetic states of nickel was investigated by using the magnetic Compton scattering method, associated with band structure calculation. Hydrogen-free, hydrogen-charged and hydrogen-discharging nickel foils were prepared in an electrochemical cell, then their magnetic Compton profiles (MCPs) were measured with circularly polarized 173 keV X-rays in magnetic fields of ±2.5 T at room temperature in situ. The MCP of the hydrogen-charged nickel was separated into the respective profiles of α-phase NiH0.03 and β-phase NiH0.7. The MCP of the β-phase NiH0.7 indicates that this hydride is weakly ferromagnetic with a small spin moment µ<0.1 µB/Ni where the positive d-like component is nearly cancelled out by the negative s,p-like component. The band structure calculation yields such a small moment in the hydrogen-ordered NiH0.75, but smaller absolute values of the d-like and the sp-like components than the observed ones.

Temperature-Dependent Orbital Degree of Freedom of a Bilayer Manganite by Magnetic Compton Scattering

We have measured temperature-dependent magnetic Compton profiles (MCPs) from a single crystal of La1.2Sr1.8Mn2O7. The MCPs, which involved the scattering of circularly polarized x rays, are in general related to the momentum density of all the unpaired spins in the system. Nevertheless, we show that when the x-ray scattering vector lies along the [110] direction, the number of magnetic electrons of a specific symmetry, i.e., d electrons of x(2)-y(2) symmetry, yield a distinct signature in the MCP, allowing us to monitor substantial changes in the occupancy of the dx(2)(-y(2)) states over the investigated temperature range of 5-200 K. This study indicates that magnetic Compton scattering can provide a powerful window on the properties of specific magnetic electrons in complex materials.