Verification of Anderson Superexchange in MnO via Magnetic Pair Distribution Function Analysis andab initioTheory

Abstract

We present a temperature-dependent atomic and magnetic pair distribution function (PDF) analysis of neutron total scattering measurements of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. The known antiferromagnetic ground-state structure fits the low-temperature data closely with refined parameters that agree with conventional techniques, confirming the reliability of the newly developed magnetic PDF method. The measurements performed in the paramagnetic phase reveal significant short-range magnetic correlations on a ∼1 nm length scale that differ substantially from the lowtemperature long-range spin arrangement. Ab initio calculations using a self-interaction-corrected local spin density approximation of density functional theory predict magnetic interactions dominated by Anderson superexchange and reproduce the measured short-range magnetic correlations to a high degree of accuracy. Further calculations simulating an additional contribution from a direct exchange interaction show much worse agreement with the data. The Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.

Transition Metal Adsorbed-Doped ZnO Monolayer: 2D Dilute Magnetic Semiconductor, Magnetic Mechanism, and Beyond 2D

“…This phenomenon is different from the ferromagnetic coupling in a Co-doped ZnO(M) sheet, which is mainly guided by a direct exchange interaction without any additional defect as reported by Schmidt et al 29 However, such a local superexchange interaction is also different from the bulk phase of MnO, where the electron coupling in the entire crystal happens completely through oxygen. 30,31 In Figure 2b, significant interactions can also be found among the neighboring Mn, O, and Mn atoms. Direct electron density overlap between two Mn atoms is identified, similar to the direct exchange between Mn atoms in a Mn dimer, 16 but it produces broken symmetry.…”

Spatial Bunching of Same-Index Polarization Singularities in Two-Dimensional Random Vector Waves

“…Given a C point, this function describes how the density of the surrounding C points varies as a function of distance. This method is widely used to describe the physics of discrete systems [44][45][46][47][48][49], it can be directly related to the structure factor [50], and it represents a spatial analogous of the degree of second-order coherence g (2) (τ ), commonly used to determine photon bunching and antibunching [51]. Figure 4 presents the pair correlation function for C points in two-dimensional random light, as obtained from our experimental data.…”

Structure of Manganese Oxide Nanoparticles Extracted via Pair Distribution Functions

“…It is clear that other methods are needed for a complete understanding of the structure of nanoparticles.High-energy XRD (HE-XRD) measurements combined with a Pair Distribution Function (PDF) analysis can yield valuable information on the short-range atomic ordering of nanocrystalline materials with some degree of structural coherence and periodicity. A large body of literature [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] details how the PDF analysis can enable a complete structural investigation of a nanostructured material. Application to nanomaterials, however, has become practical only recently, with the advent of high-flux and high-energy synchrotron radiation sources.…”