Anti-symmetric Compton scattering in LiNiPO4: Towards a direct probe of the magneto-electric multipole moment

Background: Magnetoelectric multipoles, which break both space-inversion and time-reversal symmetries, play an important role in the magnetoelectric response of a material. Motivated by uncovering the underlying fundamental physics of the magnetoelectric multipoles and the possible technological applications of magnetoelectric materials, understanding as well as detecting such magnetoelectric multipoles has become an active area of research in condensed matter physics. Here we employ the well-established Compton scattering effect as a possible probe for the magnetoelectric toroidal moments in LiNiPO4. Methods: We employ combined theoretical and experimental techniques to compute as well as detect the antisymmetric Compton profile in LiNiPO4. For the theoretical investigation we use density functional theory to compute the anti-symmetric part of the Compton profile for the magnetic and structural ground state of LiNiPO4. For the experimental verification, we measure the Compton signals for a single magnetoelectric domain sample of LiNiPO4, and then again for the same sample with its magnetoelectric domain reversed. We then take the difference between these two measured signals to extract the antisymmetric Compton profile in LiNiPO4. Results: Our theoretical calculations indicate an antisymmetric Compton profile in the direction of the ty toroidal moment in momentum space, with the computed antisymmetric profile around four orders of magnitude smaller than the total profile. The difference signal that we measure is consistent with the computed profile, but of the same order of magnitude as the statistical errors and systematic uncertainties of the experiment. Conclusions: While the weak difference signal in the measurements prevents an unambiguous determination of the antisymmetric Compton profile in LiNiPO4, our results motivate further theoretical work to understand the factors that influence the size of the antisymmetric Compton profile, and to identify materials exhibiting larger effects.

Electron Momentum Density of Nanoparticles ZrO2: A Compton Profile Study

This work investigates the electronic momentum density (EMD) distribution in nanosize zirconia (ZrO2) using the technique of Compton scattering. The ZrO2 nanoparticles (11.2[Formula: see text]nm) are synthesized of mechanical milling and characterized by SEM, XRD and TEM probes. The Compton profile [Formula: see text] of nanoZrO2 is measured by Compton spectrometer 59.54[Formula: see text]KeV Gamma rays (Americium-241) source. The study finds out that EMD in nanoZrO2 is narrower comparing in case bulk ZrO2. This study adopts the ionic-model-based free atom [Formula: see text] calculation for many configurations (Zr)[Formula: see text](O[Formula: see text])2 ([Formula: see text]) to measure the charge transfer (CT) on the compound formation. According to this study’s findings, CT values in these materials are ranged from 1.5 to 1.0 electrons from Zr to O atom.

Compton profile of few-layer graphene investigated by electron energy-loss spectroscopy

In this paper, acquisition of the valence Compton profile of few-layer graphene using electron energy-loss spectroscopy at large scattering angle is reported. The experimental Compton profile is compared with the corresponding theoretical profile, calculated using the full-potential linearized augmented plane wave method based on the local-density approximation. Good agreement exists between the theoretical calculation and experiment. The graphene profile indicates a substantially greater delocalization of the ground state charge density compared to that of graphite.

Signatures of the differential Klein‐Nishina electronic cross section in Compton's quantum theory of scattering of radiation

Here, we consider the problem of separating the relative contributions of kinematics and dynamics to the differential Klein‐Nishina electronic cross section using graphical and numerical analysis. We show that the values of the energy of scattered photons, and hence the kinetic energy of recoiled electrons calculated from Compton's quantum theory of scattering of radiation, show a degree of matching that increases with the increase in incident photon energy as quantified by chi-square goodness of fit test, with the calculated differential Klein‐Nishina electronic cross section per electron per unit solid angle for the scattering of an unpolarized photon by a stationary free electron, when appropriate normalization procedures are invoked. There is a high degree of matching in a regime where the total electronic Klein‐Nishina cross section for the Compton scattering on a free stationary electron scales as the inverse of the incident photon energy and the contribution of the electro-magnetic interaction to differential electronic cross section diminishes. Hence the third level explanation of Compton effect by quantum electrodynamics has a degree of matching with the first level of Compton's quantum theory. The degree of mismatch is an indicator of the relative contribution of dynamics to differential Klein‐Nishina electronic cross section compared to kinematics. For incident photon energies less than 1 MeV, we obtain the values of the scattering angles at which calculated differential cross section is nonzero but is kinematically limited which may lead to broadening of Compton profile. At the scattering angle where the differential cross section value is minimum for a given incident photon energy, we obtain the relative contribution of dynamics to the differential cross section compared to kinematics. Therefore, these predictions which need to be confirmed experimentally have significance to the understanding of the mechanisms of photon‐electron interactions in the Compton scattering.