Magnetization-induced Second Harmonic Generation Research Articles

Observing soft x-ray magnetization-induced second harmonic generation at a heterojunction interface

Second harmonic generation (SHG) spectroscopy in the visible and infrared regions has been a useful tool to selectively probe electronic properties at surfaces and interfaces. By examining variation of SHG under a magnetic field, one can also evaluate magnetic properties at the surfaces/interfaces. When multiple elements are involved in SHG, however, it is difficult to separate their contributions. In order to meet the demand of studying increasingly complex magnetic multilayer materials, element selectivity is desired. Here, using an Fe-based multilayer sample with broken inversion symmetry, we present observation of magnetization-induced SHG in the soft x-ray regime around the Fe M-shell absorption edge. Significant variation of SHG signal was captured depending on the direction of the magnetic moment, assuring sensitivity of the measurement likely enhanced by the Fe M-edge inner-shell resonance. The present methodology paves the way for element specific studies of magnetic properties at buried interfaces.

Magnetization‐Induced Second Harmonic Generation (MSHG) in a Pentacyanidonitrosylmolybdate‐Based Piezoelectric Ferrimagnet

The pentacyanidonitrosylmetalate [M(CN)5(NO)] (M = metal ion) is an attractive building block for bimetal assemblies exhibiting a long‐range magnetic ordering. In this work, a cyanido‐bridged bimetal assembly based on a pentacyanidonitrosylmolybdate, Cs1.26Mn0.87[Mo(CN)5(NO)]·0.6H2O, was prepared. This compound has a noncentrosymmetric cubic crystal structure in the F43m space group and a lattice constant of 10.8970(3) Å. It exhibits ferrimagnetism with a Curie temperature (TC) of 65 K due to the antiparallel ordering of the MnII (S = 5/2) and MoI (S = 1/2) magnetic spins. Owing to the piezoelectric crystal structure, this compound exhibits second harmonic generation (SHG) and magnetization‐induced second harmonic generation (MSHG).

Nonlinear magneto-plasmonics

Nonlinear magneto-plasmonics (NMP) describes systems where nonlinear optics, magnetics and plasmonics are all involved. In such systems, nonlinear magneto-optical Kerr effect (nonlinear MOKE) plays an important role as a characterization method, and Surface Plasmons (SPs) work as catalyst to induce many new effects. Magnetization-induced second-harmonic generation (MSHG) is the major nonlinear magneto-optical process involved. The new effects include enhanced MSHG, controlled and enhanced magnetic contrast, etc. Nanostructures such as thin films, nanoparticles, nanogratings, and nanoarrays are critical for the excitation of SPs, which makes NMP an interdisciplinary research field in nanoscience and nanotechnology. In this review article, we organize recent work in this field into two categories: surface plasmon polaritons (SPPs) representing propagating surface plasmons, and localized surface plasmons (LSPs), also called particle plasmons. We review the structures, experiments, findings, and the applications of NMP from various groups.

Nanometer-size hard magnetic ferrite exhibiting high optical-transparency and nonlinear optical-magnetoelectric effect.

Development of nanometer-sized magnetic particles exhibiting a large coercive field (Hc) is in high demand for densification of magnetic recording. Herein, we report a single-nanosize (i.e., less than ten nanometers across) hard magnetic ferrite. This magnetic ferrite is composed of ε-Fe2O3, with a sufficiently high Hc value for magnetic recording systems and a remarkably high magnetic anisotropy constant of 7.7 × 106 erg cm−3. For example, 8.2-nm nanoparticles have an Hc value of 5.2 kOe at room temperature. A colloidal solution of these nanoparticles possesses a light orange color due to a wide band gap of 2.9 eV (430 nm), indicating a possibility of transparent magnetic pigments. Additionally, we have observed magnetization-induced second harmonic generation (MSHG). The nonlinear optical-magnetoelectric effect of the present polar magnetic nanocrystal was quite strong. These findings have been demonstrated in a simple iron oxide, which is highly significant from the viewpoints of economic cost and mass production.

Magnetization Processes Study in the Implanted Garnet Films Using the Second-Harmonic Generation Effect

In the work, magnetization-induced second-harmonic generation (MSHG) effect has been appliedto investigate the magnetization distribution changes, induced by ion implantation into thethin surface layer of garnet film.The studies were performed on the (111)-orientedepitaxial garnet film (YSmLuCa)$_3$(FeGa)$_5$O$_{12}$ implanted with $1.5\times10^{16}$~cm$^{-2}$dose of H$_2^+$ ions at $60$~keV energy. The measurements of the MSHG effectwere performed as a function of amplitude of perpendicular external magnetic field. The observed complex field dependencesof the remagnetization processes for the implanted garnet film studied were described in theframe of a phenomenological model developed. The model of the MSHG effect allows to performdecomposition of measured dependences on separate contributions originating from magnetizationcomponents related to implanted and unimplanted film volumes.

Vectorial magnetometry with second-harmonic generation effect in studies of implantation induced inhomogeneity in garnet films

The magnetization-induced second-harmonic generation (MSHG) effect was applied to study changes of magnetization distribution caused by H2+ ions implantation in magnetic garnet film of (111) symmetry. The evolution of the magnetization vector m in perpendicular magnetic field H was studied as a function of coherently rotated polarizers by an angle φ. The I2ω(H,φ) intensities exhibit completely different character as compared to the unimplanted film. The experimental results were explained in the frame of a phenomenological model of the MSHG effect, developed for the structure of 3m symmetry, composed of implanted and unimplanted sublayers. The theoretical approach allowed to determine the amplitudes and phases of nonlinear optical susceptibility tensor elements χ[2] as well as the m(H) vector components. In contrast to the linear magneto-optical Faraday effect, application of nonlinear MSHG method allows for simultaneous determination of all components of the magnetization vector in single experiment. It ...

Second-Harmonic Generation Studies of Inhomogeneous Magnetization Distributions in Thin Garnet Film

The magnetization processes can be e ectively studied using magnetization-induced second-harmonic generation e ect (MSHG). The aim of the current work is the investigation of inhomogeneous magnetization distributions induced in the surface area of the garnet lm by ion implantation. The studies were performed on magnetic garnet lm of (111) symmetry, implanted with H+2 ions of 1.5 × 10 cm−2 dose and 60 keV energy. The measurements of MSHG e ect were performed as a function of the sample rotation angle and the amplitude of external magnetic eld. The observed MSHG intensity hystereses were subjected to a decomposition procedure into contributions having di erent magnetic eld dependences. The contributions originating from the implanted and unimplanted parts of the lm volume of di erent magnetic ordering were analyzed and discussed.

First and second order in magnetization effects in optical second-harmonic generation from a trilayer magnetic structure

Linear and nonlinear optical properties of a thin planar CoFe/Al2O3/CoFe structure for different angles of incidence of the fundamental radiation are studied by means of the magneto-optical Kerr effect and magnetization-induced second-harmonic generation (SHG). The composition of this multilayered structure supports the appearance of the antiferromagnetic state, which leads to nonreciprocal optical effects and is discussed in terms of the magnetic toroid moment. We show that in accordance with the phenomenological description, SHG magnetic hysteresis loops for a linearly polarized pump beam are determined by linear in magnetization M components of the SHG polarization, while for a circularly polarized pump such a description necessarily involves both linear and quadratic in M components of the nonlinear polarization. Symmetry analysis of the magnetization-induced SHG supports the differences between the cases of linear and circular polarization of the incident radiation observed in the experiment, as well as a partial suppression of first in magnetization SHG contributions. Relative values of the linear and quadratic in magnetization components of the SHG polarization are estimated for the trilayer structure and for a reference homogeneous ferromagnetic film.

Second-Harmonic Generation from a Magnetic Buried Interface Enhanced by an Interplay of Surface Plasma Resonances

Magnetization-induced second-harmonic generation (SHG) enhanced by surface plasma resonances (SPRs) is studied in a Au/(Bi,Tm) iron garnet (IG) perforated magnetoplasmonic crystal capable of sustaining SPRs at both air/Au and Au/(Bi,Tm)IG interfaces. Asymmetry of a crossing point of the SPR branches is shown, demonstrating a significant difference in the SHG spectra at both sides of the complex resonance. Despite the thick (120 nm) Au layer, the sensitivity of the SHG to the SPR at the buried Au/garnet interface is demonstrated through observing an SHG magnetic contrast, when the SHG is amplified by an excitation of the SPR at the bottom interface.

Multifunctional Material: Bistable Metal–Cyanide Polymer of Rubidium Manganese Hexacyanoferrate

Abstract Since phase-transition phenomena in solid-state materials can change the magnetic, electrical, and optical properties with external stimuli, they are attracting widespread attention from the viewpoints of both fundamental science and practical applications. We have synthesized various cyano-bridged metal complexes possessing anomalous bistabilities that exhibit unprecedented phase transition phenomena. This paper focuses on rubidium manganese hexacyanoferrate, RbxMn[Fe(CN)6](x+2)/3·zH2O, which is a Prussian blue analogue. Here, the unique functionalities of rubidium manganese hexacyanoferrate are described: a charge-transfer-induced phase transition, control of the thermal hysteresis loop, and a huge thermal hysteresis with a hidden stable phase are presented as thermally-induced phase-transition phenomena, while a photoinduced phase collapse is described as a novel photoinduced phase-transition phenomenon. A one-shot-laser-induced charge-transfer phase transition is displayed as a photoinduced phase-transition phenomenon at ambient temperature. Moreover, second harmonic generation (SHG) and magnetization-induced second harmonic generation (MSHG) are provided as correlation effects between the optical and dielectrical properties. Finally, a one-shot-laser-induced photo-demagnetization and reversible photomagnetic switching between ferromagnetism and antiferromagnetism are demonstrated as photomagnetic effects.

Magneto-optical spectroscopy of surface/interfaces in Co/garnet heterostructures

Abstract Here we report on combined linear and nonlinear magneto-optical studies of Co/garnet heterostructures. Both the crystallographic symmetry and the magnetization of buried Co/garnet interfaces were deduced from an analysis of the rotational anisotropy of spectroscopic magnetization-induced second-harmonic generation (MSHG) measured in the transverse (Voigt) geometry. Unexpected non-zero components of the magnetic MSHG tensor were found, that do not correspond to the original 4mm point group symmetry of (0 0 1)-plane oriented garnet layers. They may be tentatively assigned to the anisotropic distribution of the Co impurities. For Co/garnet interfaces, the magnetic MSHG contrast shows a maximum at the fundamental wavelength of about 890 nm which can be correlated with Faraday rotation spectra at the second harmonic frequency.

Characterization of Nanostructured Plasmonic Surfaces with Second Harmonic Generation

Because of its high surface and interface sensitivity, the nonlinear optical technique of second harmonic generation (SHG) is a designated method for investigating nanostructured metal surfaces. Indeed, the latter present a high surface-to-volume ratio, but even more importantly, they can exhibit strong near-field enhancements or "hot spots". Hot spots often appear as a result of geometric features on the nanoscale or surface plasmon resonances, which are collective electron oscillations on the surface that, on the nanoscale, can readily be excited by light. In the last 10 years, near-field hot spots have been responsible for dramatic developments in the field of nano-optics. In this Feature Article, the influence of hot spots on the SHG response of nanostructured metal surfaces is discussed on both the microscopic and macroscopic levels. On the microscopic level, the nanostructured metal surfaces were characterized by scanning SHG microscopy, complemented by rigorous numerical simulations of the near-field and of the local electric currents at the fundamental frequency. On the macroscopic level, SHG-circular dichroism and magnetization-induced SHG characterization techniques were employed.

Characterization of magnetization-induced second harmonic generation in iron oxide polymer nanocomposites

We have measured the magnetization-induced second harmonic generation (MSHG) of a nanocomposite consisting of iron oxide nanoparticles in a polymer film. The existing theoretical framework is extended to include DC magnetic fields in order to characterize the MSHG signal and analyze the measurements. Additionally, magnetic hysteresis loops are measured for four principal polarizer-analyzer configurations, revealing the P(IN)-P(OUT) and S(IN)-P(OUT) polarizer-analyzer configurations to be sensitive to the transverse magnetic field. These results demonstrate the use of MSHG and the applied formalism as a tool to study magnetic nanoparticles and their magnetic properties.

Surface nonlinear optics and nonlinear magneto-optics at Moscow State University [Invited

In this paper, we present a brief review of the launch of surface nonlinear optics and nonlinear magneto-optics at Moscow State University in the 1980s and further development of these areas in Russia. The history of these branches of modern nonlinear optics cannot be separated from the history of Russia’s School of Nonlinear Optics founded by Rem V. Khokhlov and his colleagues and partners Sergey A. Akhmanov and David N. Klyshko. After a brief description of the basic contributions of the founding fathers, we present retrospection of surface nonlinear-optical and magneto-optical studies performed at the Physics Department of Moscow State University. In the last section, we present results of our recent studies of the relation between surface plasmons and magnetization-induced second-harmonic generation in magnetic nanoparticles.

Light-induced change in magnetization-induced second harmonic generation of Fe0.52Rh0.48 films

Irradiating with pulsed laser light induces high-speed optical switching of surface magnetization-induced second harmonic generation (MSHG) in Fe0.52Rh0.48 thin films at room temperature. The second harmonic rotation angle (θSH) of 25.0° was recorded in the irradiated film at 2000 Oe. This θSH value is as much as 740 times larger than the normal Kerr rotation angle (0.034° at 388 nm). The observed gigantic θSH value is attributed to surface MSHG on the ferromagnetic phase in Fe0.52Rh0.48, which is generated by the optical heating.

ChemInform Abstract: A Decade of Octacyanides in Polynuclear Molecular Materials

AbstractReview: about 170 refs.

A Decade of Octacyanides in Polynuclear Molecular Materials

AbstractThe aim and the scope of this review is to show the results of ten years of research following the first reports on magnetic and photomagnetic assemblies constructed from [M(CN)8]n–. It is illustrated on the basis of our own work as well as a wide range of studies carried out in numerous laboratories around the world. The diversity and evolution of topological and structural patterns is discussed alongside synthetic strategies, which led to the establishment of regular magnetostructural correlations in selected 3D systems. Different types of functionality observed in solid phases are presented with special attention devoted to tuning of magnetic properties by physical and chemical stimuli. Examples of advanced properties discovered in octacyanometallate‐based magnetic materials comprise SMMs (single molecule magnets) and SCMs (single chain magnets), nonlinear effects MSHG (magnetization‐induced second harmonic generation) and chirality, SCO (spin crossover) and luminescence. The potential of the development of octacyanometallate‐based coordination assemblies towards addressable, multifunctional molecular materials for future application is discussed.

Multifunctional Magnetic Molecular {[MnII(urea)2(H2O)]2[NbIV(CN)8]}n System: Magnetization-Induced SHG in the Chiral Polymorph

Incorporation of urea molecules into the magnetic system MnII-[NbIV(CN)8] results in formation of two magnetic polymorphs {[MnII(H2O)(urea)2]2[NbIV(CN)8]}n chiral α and centric β crystallizing in space groups P41 and P1̅, respectively. Both polymorphs exhibit extremely similar structures and are soft ferrimagnets with critical temperatures of 43 and 42 K, respectively. The presence of coordinated urea in the noncentrosymmetric α produces NLO functionality, second harmonic generation (SHG), whereas centric β is just another molecular magnet. As a result of interaction of both functionalities below magnetic ordering temperature, the magnetization-induced SHG (MSHG) is observed for polymorph α. The observed MSHG/SHG signal ratio was the largest among molecule-based noncentrosymmetric magnets. The presence of urea molecules in both polymorphs gives also rise to their interesting topotactic reactivity. Both polymorphs can be easily transformed into a new entity {[MnII(H2O)]2[NbIV(CN)8]·2.5MeOH}n 2b with significant shift of critical temperature Tc to 70 K. Subsequent hydration of 2b leads to {[MnII(H2O)2]2[NbIV(CN)8]·4H2O}n 3 with Tc of 47 K.

Plasmons Reveal the Direction of Magnetization in Nickel Nanostructures

We have applied the surface-sensitive nonlinear optical technique of magnetization-induced second harmonic generation (MSHG) to plasmonic, magnetic nanostructures made of Ni. We show that surface plasmon contributions to the MSHG signal can reveal the direction of the magnetization. Both the plasmonic and the magnetic nonlinear optical responses can be tuned; our results indicate novel ways to combine nanophotonics, nanoelectronics, and nanomagnetics and suggest the possibility for large magneto-chiral effects in metamaterials.

Large Magnetization-Induced Second Harmonic Generation in an Enantiopure Chiral Magnet

The absence of centrosymmetry in the enantiopure chiral magnet [N(CH(3))(n-C(3)H(7))(2)(C*H(CH(3))C(2)H(5))][Mn(II)Cr(III)(ox)(3)] allows the observation of bulk second harmonic generation (SHG) in this material. At low temperature, the onset of magnetization gives birth to a magnetization-induced SHG (MSHG) contribution. With an angular shift of 13.1 degrees upon magnetization reversal, the MSHG effects appear to be much larger than the corresponding linear magneto-optical effects. Thanks to the single-crystalline state of the sample, the variation of the signal with the orientation of the magnetic field and/or the angle between the polarization of the incident radiation and the outgoing SHG signal in the paramagnetic and ferromagnetic phases is reproduced and well-understood through the use of a symmetry-based analysis of the nonlinear susceptibility tensor.