Measuring the magnetic configuration at complex buried layers and interfaces is an important task, which requires especially a non-destructive probing technique. X-ray resonant magnetic reflectometry ...(XRMR) combines the non-destructive depth profiling potential of x-ray reflectometry with the excellent sensitivity for magnetic phenomena, utilizing the x-ray magnetic circular dichroism effect. It provides the magnetic spatial distribution with a precision down to the angstrom scale, combined with element and symmetry specificity, sub-monolayer sensitivity, and the possible separation of spin and orbital magnetic moments. This review provides an overview to the XRMR technique in a tutorial way. We focus on the introduction to the theory, measurement types, and data simulation. We provide related experimental examples and show selected applications.
Abstract
The discovery of two-dimensional magnets has initiated a new field of research, exploring both fundamental low-dimensional magnetism, and prospective spintronic applications. Recently, ...observations of magnetic skyrmions in the 2D ferromagnet Fe
3
GeTe
2
(FGT) have been reported, introducing further application possibilities. However, controlling the exhibited magnetic state requires systematic knowledge of the history-dependence of the spin textures, which remains largely unexplored in 2D magnets. In this work, we utilise real-space imaging, and complementary simulations, to determine and explain the thickness-dependent magnetic phase diagrams of an exfoliated FGT flake, revealing a complex, history-dependent emergence of the uniformly magnetised, stripe domain and skyrmion states. The results show that the interplay of the dominant dipolar interaction and strongly temperature dependent out-of-plane anisotropy energy terms enables the selective stabilisation of all three states at zero field, and at a single temperature, while the Dzyaloshinksii-Moriya interaction must be present to realise the observed Néel-type domain walls. The findings open perspectives for 2D devices incorporating topological spin textures.
We analyze a stylized distribution channel (bilateral monopoly) model where an upstream manufacturer sells output to a downstream retailer. In a two-stage linear demand game setting, we show that a ...two-part contract, consisting of a wholesale price and corporate social responsibility (CSR) component, can be utilized by the manufacturer to fully coordinate and control its retailer. Thus, a CSR contract can be used in place of the traditional two-part tariff scheme (wholesale price and fixed franchise fee) to optimally coordinate the marketing channel. Our model provides a novel theoretical profit-maximizing rationale for the strategic use of CSR.
We analyze a simple linear demand bilateral monopoly situation where one of the firms, either the up-stream manufacturer or the down-stream retailer, is socially concerned in terms of its desire to ...enhance its end-customers’ welfare in addition to the traditional profit motive. Two cases are explored: the up-stream producer exhibits corporate social responsibility (CSR) in one case and the down-stream retailer in the other. In the two-stage game, the retailer makes their quantity-setting decision in stage-two, given the two-part tariff (wholesale price and fixed franchise fee) set by the stage-one producer. In this setting, among other things, we find that the optimal channel-coordinating tariff is very different from the standard pure profit-maximizing two-part tariff. For example, if either firm in the supply/marketing chain exhibits CSR, we show the optimal wholesale price does not equal the manufacturer’s marginal production cost, nor does the fixed fee equal the monopoly profit earned by the retailer. Finally, we find that our two-part tariff CSR model provides a theoretical rationale for the empirical finding of little to no correlation between CSR and firm profits.
► We analyze a bilateral monopoly where one firm is socially concerned. ► The coordinating tariff is very different from the standard two-part tariff. ► The optimal wholesale price does not equal the producer’s marginal cost. ► The optimal fixed fee does not equal the profit earned by the retailer. ► This helps explain the lack of correlation between social concern and firm profits.
Abstract
Interface engineering in complex oxide superlattices is a growing field, enabling manipulation of the exceptional properties of these materials, and also providing access to new phases and ...emergent physical phenomena. Here we demonstrate how interfacial interactions can induce a complex charge and spin structure in a bulk paramagnetic material. We investigate a superlattice (SLs) consisting of paramagnetic LaNiO
3
(LNO) and highly spin-polarized ferromagnetic La
2/3
Ca
1/3
MnO
3
(LCMO), grown on SrTiO
3
(001) substrate. We observed emerging magnetism in LNO through an exchange bias mechanism at the interfaces in X-ray resonant magnetic reflectivity. We find non-symmetric interface induced magnetization profiles in LNO and LCMO which we relate to a periodic complex charge and spin superstructure. High resolution scanning transmission electron microscopy images reveal that the upper and lower interfaces exhibit no significant structural variations. The different long range magnetic order emerging in LNO layers demonstrates the enormous potential of interfacial reconstruction as a tool for tailored electronic properties.
The recent claim of superconductivity above room temperature in Pb10−xCux(PO4)6O with 0.9 < x < 1 (referred to as LK-99) has sparked considerable interest. To minimize the influence of structural ...defects and impurity phases on the physical properties, we have synthesized phase-pure single crystals with a copper doping level of x ∼ 1. We find that the crystals are highly insulating and optically transparent. X-ray analysis reveals an uneven distribution of the substituted Cu throughout the sample. Temperature (T) dependent magnetic susceptibility measurements for 2 ≤ T ≤ 800 K reveal the diamagnetic response characteristic of a non-magnetic insulator, as well as a small ferromagnetic component, possibly originating from frustrated exchange interactions in Cu-rich clusters in the Pb10−xCux(PO4)6O structure. No anomalies indicative of phase transitions are observed. We, therefore, rule out the presence of superconductivity in Pb9Cu(PO4)6O crystals and provide some considerations on the origin of anomalies previously reported in experiments on polycrystalline specimens.
The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is ...well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths.
Distinguishable L
2
and L
3
edges and a clear separation into j
3/2
and j
1/2
excitations are necessary for the application of L
2,3
edge X-ray magnetic circular dichroism (XMCD) sum rules, which ...provide element-specific information about spin and orbital magnetic moments. This separation is present for the heavy transition metals (TM), like Co and Ni, due to their large L
2,3
spin-orbit splitting. However, for the light TM, the 2p spin-orbit splitting is strongly reduced and quantum mechanical mixing of j
3/2
and j
1/2
excitations is present. This mixing reduces the observed XMCD related spin and magnetic dipole term contributions and prevents the direct application of XMCD spin sum rules. A large number of 2p → 3d absorption spectra have been fitted nearly perfectly by a simple and phenomenological model, which takes into account lifetime effects and provides quantitative information about jj-mixing at the light TMs. On the basis of this mixing coefficient, sum rule correction factors have been determined. The proposed model results in renormalized magnetic projected XMCD spin moments, verified for different compounds of V, Cr, and Mn. A comparison with complementary methods gives consistent results. This or a similar fitting procedure and the estimated correction factors can be used in the future as a light element XMCD spin renormalization technique.
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