Amplitude Of External Field Research Articles

VACUUM BIREFRINGENCE AND DICHROISM IN A STRONG PLANE-WAVE BACKGROUND

In the present study, we consider the effects of vacuum birefringence and dichroism in strong electromagnetic fields. According to quantum electrodynamics, the vacuum state exhibits different refractive properties depending on the probe photon polarization and one also obtains different probabilities of the photon decay via production of electron-positron pairs. Here we investigate these two phenomena by means of several different approaches to computing the polarization operator. The external field is assumed to be a linearly polarized plane electromagnetic wave of arbitrary amplitude and frequency. Varying the probe-photon energy and the field parameters, we thoroughly examine the validity of the locally-constant field approximation (LCFA) and techniques involving perturbative expansions in terms of the external-field amplitude. Within the latter approach, we develop a numerical method based on a direct evaluation of the weak-field Feynman diagrams, which can be employed for investigating more complex external backgrounds. The polarization operator depends on two parameters: classical nonlinearity parameter ξ and the product η = ωq0/m2 of the laser field frequency ω and the photon energy q0 (m is the electron mass). The domains of validity of the approximate techniques in the ξη plane are explicitly identified.

Room-Temperature Magneto-Photoresponse in All-2D Optoelectronic Devices for In-Sensor Vision Systems.

Interplay between magnetism and photoelectric properties introduces the effective control of photoresponse in optoelectronic devices via magnetic field, termed as magneto-photoresponse. It enriches the application scenarios and shows potential to construct in-sensor vision systems for artificial intelligence with gate-free architecture. However, achieving a simultaneous existence of room-temperature magnetism and notable photoelectric properties in semiconductors is a great challenge. Here, the room-temperature magneto-photoresponse is accomplished in all-2D optoelectronic devices, employing 2D ferromagnet Fe3GaTe2 as the source and drain, with WSe2 forming the channel. The interplay between room-temperature magnetism and photoelectric properties is realized by introducing the unique magneto-band structure effect from 2D interface, resulting in magneto-tunable charge transfer between Fe3GaTe2 and WSe2. The photocurrent in this 2D optoelectronic device exhibits robust response to both the direction and amplitude of external magnetic fields. Utilizing constructed 2D optoelectronic devices with magneto-photoresponse, traditional gate-controlled phototransistors are replaced and a prototype in-sensor vision system with visual adaptation, significantly improving the recognition accuracy to over four times in low-contrast environments is established. These findings pave a way for achieving high-temperature magneto-photoresponse, thereby guiding the construction of robust in-sensor vision systems toward high performance and broad applications.

The pool boiling heat transfer of ammonia/Fe3O4 nano-refrigerant in the presence of external magnetic field and heat flux: A molecular dynamics approach

Pool boiling is distinguished by its capacity to eliminate excessive heat fluxes (HFs) at low temperatures. In recent decades, the optimal design of flooded evaporators elevated the significance of pool boiling HT with refrigerant to conserve natural resources and energy. The industry highly regards this process on account of its superior heat transfer (HT) coefficient in comparison to other HT mechanisms. Among the types of boiling, pool boiling has a special place due to its ability to remove HFs at low temperatures. This study was the first to investigate the boiling characteristics of the ammonia/Fe3O4 nano-refrigerant in a copper (Cu) nanochannel (NC) through molecular dynamics (MD) simulations. The primary goal was to investigate the effect of external HF (EHF) and external magnetic field amplitude (EMFA) on nanostructures' atomic behavior (AB) and thermal behavior (TB). The research findings indicate that increasing the applied EHF led to increased particle movement and the HT rate. By changing the EHF, boiling behavior in the nano-refrigerant may also be seen. Maximum (Max) velocity (Vel.) increased to 8.970 Å/ps when the EHF increases to 0.5 W/m2. Atomic collisions and particle mobility both increase when the EHF increases. Therefore, the maximum temperature value increases to 359.46 K. When the EMFA applied to the nano-refrigerant reaches to 0.5 T, the maximum values of the parameters, such as the Temp. and the velocity, reach to 410.07 K, and 11.802 Å/ps, respectively.

Molecular dynamics method to investigate the effect of variable electric field on the first charge of Li-Ion Nanobattery with carbon anode

Lithium-ion batteries are popular in the market due to their ability to charge and many applications in life. In these rechargeable batteries, Lithium ions move from the positive electrode to the negative electrode during charging and in the opposite direction during discharge. In the present research, the effect of external electric field amplitude (EEFA) with different ratios of 0.1, 0.2, 0.3, and 0.5 V/Å on the Li-ion-C-anode nanobattery was investigated by molecular dynamics (MD), and the effect of EEFA (0.1–0.5 V/Å) on the Mean squared displacement (MSD) was checked. It is concluded that for the Li-Li pair, the NN distance presents a slight tendency to decrease. Moreover, with the increase in the intensity of the EEFA, the number of mobile lithium ions increased from 60 to 183. Numerically, with increasing EEFA from 0.1–0.2, 0.3, and 0.5 V/Å, the MSD of lithium increased from 38.28–59.22, 89.91, and 113.04 nm2. This behaviour indicated that the lithiation of the carbon is occurring and that the lithium ions can diffuse through the carbon structure by breaking C–C bonds and forming a LiC alloy wall.

Magnetic field sensor based on a low-frequency-tail spintronic diode

Spin-torque diode have shown great potentials and performance in many applicative fields, from microwave detectors to energy harvesters. In this work, we use micromagnetic simulations to study, at room temperature, a state-of-the-art non-resonant low-frequency-tail spin-torque diode in terms of dc output voltage as a function of the amplitude of an in-plane external field applied along different directions. We find that there exists a threshold value of the injected ac current that promotes a linear behavior of the output voltage of field down to the pT range, and we suggest exploiting such a behavior for the design of a magnetic field sensor.

Numerical study for the impact of current sharing effect upon dynamic behaviour of DC-carrying HTS coils under alternating magnetic fields

Numerical characterization for the dynamic behaviour of DC-carrying HTS coils subjected to alternating magnetic fields is crucial for its design and protection. In conventional approaches, only superconducting layers are modeled. The missing current sharing effect in those models results in the overestimation of dynamic voltage/resistance. In reality, the transport current will migrate into the metal layers, and therefore the dynamic voltage/resistance is limited. In this paper, we present an equivalent modeling approach (EPM) instead of modeling the real geometry which will cost massive computation resources. The effectiveness of the approach is validated against a full-scale model containing all the layers. Then, this approach is applied to estimate the dynamic behaviour of a multiturn racetrack HTS coil. It is found that the current sharing effect mainly happens at the outer layers of the coil due to the shielding effect, and is enhanced with the increase of external field amplitude then gradually spreads to the inner layers. Moreover, the competition between the transport current and the induced current in the metal layers is observed.

Optimization of Magnetic Cobalt Ferrite Nanoparticles for Magnetic Heating Applications in Biomedical Technology.

Using magnetic nanoparticles for extracorporeal magnetic heating applications in bio-medical technology allows higher external field amplitudes and thereby the utilization of particles with higher coercivities (HC). In this study, we report the synthesis and characterization of high coercivity cobalt ferrite nanoparticles following a wet co-precipitation method. Particles are characterized with magnetometry, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy (TEM) and calorimetric measurements for the determination of their specific absorption rate (SAR). In the first series, CoxFe3-xO4 particles were synthesized with x = 1 and a structured variation of synthesis conditions, including those of the used atmosphere (O2 or N2). In the second series, particles with x = 0 to 1 were synthesized to study the influence of the cobalt fraction on the resulting magnetic and structural properties. Crystallite sizes of the resulting particles ranged between 10 and 18 nm, while maximum coercivities at room temperatures of 60 kA/m for synthesis with O2 and 37 kA/m for N2 were reached. Magnetization values at room temperature and 2 T (MRT,2T) up to 60 Am2/kg under N2 for x = 1 can be achieved. Synthesis parameters that lead to the formation of an additional phase when they exceed specific thresholds have been identified. Based on XRD findings, the direct correlation between high-field magnetization, the fraction of this antiferromagnetic byphase and the estimated transition temperature of this byphase, extracted from the Mössbauer spectroscopy series, we were able to attribute this contribution to akageneite. When varying the cobalt fraction x, a non-monotonous correlation of HC and x was found, with a linear increase of HC up to x = 0.8 and a decrease for x > 0.8, while magnetometry and in-field Mössbauer experiments demonstrated a moderate degree of spin canting for all x, yielding high magnetization. SAR values up to 480 W/g (@290 kHz, 69 mT) were measured for immobilized particles with x = 0.3, whit the external field amplitude being the limiting factor due to the high coercivities of our particles.

Magnetization dynamics in layered systems with coexisting bilinear and biquadratic interlayer exchange coupling

Important aspects of exchange-coupled magnetic layered structures are related to the noncollinear arrangement of sublayer magnetizations which can arise from competition between bilinear (BL) and biquadratic (BQ) interlayer exchange coupling (IEC). In this work, the influence of coexisting BL and BQ IEC of different strengths on magnetization precession in layered systems is investigated both experimentally and theoretically. Laser-induced magnetization precession has been studied in the $\text{Fe/Si}({d}_{\text{Si}}$) multilayers (MLS) as a function of the amplitude ($H$) and orientation angle (${\ensuremath{\theta}}_{H}$) of external magnetic field using time-resolved magneto-optical Kerr (TRMOKE) effect. Strongly changing characters of precession frequency dependencies $\ensuremath{\omega}(H,{\ensuremath{\theta}}_{H})$ for Fe sublayer thickness ${d}_{\text{Fe}}=3$ nm and Si spacer-layer thicknesses (${d}_{\text{Si}}$) varying in the range of 0.9--2.4 nm have been observed. Analytical formulas for acoustic and optic mode dispersion relations with coexisting BL and BQ IEC, scaled by ${J}_{1}$ and ${J}_{2}$ parameters, respectively, for the in-plane effective magnetic anisotropy and arbitrary magnetic field direction were derived, and very good agreement with the experimentally observed frequency dependencies has been obtained. It is shown that BQ coexisting with BL IEC significantly influences on the magnitude and form of dispersion relations. From analytical formula derived, it follows that zero-field optical mode frequency tends to zero as $|{J}_{1}|$ approaches $2{J}_{2}$. The acoustic and optic mode-crossing effect has been observed and it is found that values of crossing fields and frequency gaps strongly increase as ${\ensuremath{\theta}}_{H}$ angles decrease and depend on relative BL and BQ IEC strengths. The BL IEC is of ferromagnetic type with ${J}_{1}\ensuremath{\approx}1.6$ mJ/${\mathrm{m}}^{2}$ for the MLS with ${d}_{\text{Si}}=0.9$ nm, and changes to antiferromagnetic one with ${J}_{1}\ensuremath{\approx}\ensuremath{-}0.9$ mJ/${\mathrm{m}}^{2}$ for the MLS with ${d}_{\text{Si}}=1.4$ nm, while the ${J}_{2}$ parameter of BQ IEC decreases from 1.8 to 1.0 mJ/${\mathrm{m}}^{2}$. The coupling strengths decrease by one to two orders of magnitude for the sample with ${d}_{\text{Si}}=2.4$ nm, but both mode frequencies are still observed and well reproduced by the theory. It is shown that ${J}_{1}$ and ${J}_{2}$ parameters obtained in the TRMOKE experiment coincide within the estimated error bars with the determined from independent measurements of magnetization processes in the static magneto-optical Kerr effect and interpreted with the use of analytical formulas derived. Numerical solutions of coupled Landau-Lifshitz-Gilbert (LLG) equations for acoustic and optic modes, with inclusion of BL IEC, intrinsic Gilbert damping, and spin-pumping damping terms, and extended to include BQ IEC, were performed and fitted to experimental data. It is shown that determined effective damping coefficients on $H$ and ${\ensuremath{\theta}}_{H}$ dependencies for acoustic and optic modes are very well simulated with the use of LLG equation solutions with Gilbert damping, spin-pumping-damping--related effective spin-mixing conductance, and spin-diffusion length parameters included. The dependencies of the parameters on ${d}_{\text{Si}}$ spacer-layer thickness are discussed and compared with available data for other systems.

Investigation on thermal effect of bulk high-temperature superconductors under varying external magnetic field

Superconducting bulks applied to high-temperature superconducting (HTS) maglev vehicles are susceptible to magnetic field, resulting in alternating current (AC) losses and heat generation, which affect the stability of the suspension system. Therefore, the thermal effect of superconducting bulk under external magnetic field is worth studying. The paper uses finite element software to establish a 2D electromagnetic-thermal coupling model. The distribution and variation of HTS bulks’ temperature under varying external magnetic field are simulated and analyzed, and the loss and temperature rise of rectangular bulks with different thicknesses are studied. Finally, the effect of increasing the critical current density on the thermal effect of the superconducting bulk is discussed. The results show that the temperature rise of bulk has a positive correlation with the amplitude and frequency of external magnetic field. The maximum temperature is affected by the angle of magnetic field. Under the same external magnetic field, the bulk with smaller thickness produces smaller loss and temperature rise. The research results can provide important references for the operation and furniture design of HTS maglev vehicles.

A molecular dynamics study of thermal behavior of ammonia/Cu nanorefrigerant flow under different initial pressures and electric fields

In today’s world, energy consumption was increased dramatically. This increase in consumption has led to many advances in heat transfer (HT) and phase change (PC) in mechanicalprocesses. This study investigates the thermal conductivity (TC) and PC of Cu-Ammonia nano-refrigerant (NR). This study uses the molecular dynamics (MD) method in an aluminium nanochannel (NC). This simulation examines the effect of external electric field amplitude (EFA) and the initial pressure (IP) on atomic (temperature (T) and density (D) profiles) and thermal properties (TP) of the NR. The kinetic energy (KE) and total energy (TE) are examined to appraise the stability process. The results show that increasing the IP to 5 bar increases the maximum density value to 0.03 atoms/Å3, which indicates an improvement in the sample's atomic properties (AP). The PC particle rate increases with increasing IP from 53 to 59%. Also, increasing the IP decreases PC duration (from 2.96 to 2.89 ns) and increases the TC (0.76 to 0.80 W/m K). On the other hand, by investigating the increase in the applied EFA to the NR from 1 to 5 Å, the maximum density increases from 0.028 to 0.029 atoms/Å3, and the rate of PC particles decreases to 49%. Also, an increase in the EFA causes an increase in the PC duration and a reduction in TC in the sample.

Characterisation of surface charge density and net electric field during parallel-plate dielectric barrier discharge generated in atmospheric-pressure air

We measured the surface charge density in a parallel-plate dielectric barrier discharge (DBD) using the Pockels effect, and the axial and lateral components of the net electric field were evaluated for different gap lengths and applied voltages. The DBD was driven by a 5 kHz sinusoidal voltage in gap lengths of 0.5, 0.3, and 0.1 mm at atmospheric pressure with Bi4Ge3O12 crystal as a dielectric. Typical microdischarges (MDs) were observed for every gap length, and the number of MDs increased with the increasing applied voltage. As the gap length decreased, the spot radius of a single MD decreased, whereas the peaks of charge density were almost the same, indicating that the amount of charge transported per unit MD is limited for short gaps. The spatial memory effect, in which MDs occur at the same position in successive cycles, was not always observed under the experimental conditions, and it was evaluated considering the surface charge density distributions. Whether the memory effect works is determined by the surface charge density, and it is likely to occur under a balance between positive and negative charges across successive half-cycles. The net electric field was estimated from surface charge measurements. The axial component of the net electric field strength increased up to 150–170 Td before the MD occurred, and it decreased below 100 Td by the surface charge deposited by MD, being approximately 50%–60% of the external field amplitude. The maximum value of the lateral component of the electric field was approximately 150 Td at the edge of the MD spot with a gap length of 0.5 mm, and it decreased as the gap length decreased. As a negative surface charge generated a weaker lateral field than a positive one, the electric field distribution differed between anodic and cathodic dielectrics.

Molecular dynamics study of the effect of external electric field amplitude and cavity on thermal properties of Ammonia/Copper Nano-Refrigerant

With the ever-increasing energy costs, the need to improve the efficiency of cooling systems, reduce costs, and optimize the design is usually the first goal for system designers. One way to improve these systems is to use nano-refrigerants (NRs). This study simulates the thermal manner of ammonia refrigerant with Cu nanoparticles (NPs) in a nanochannel (NC) by calculating parameters such as velocity (V) and temperature (T) profiles, aggregation time (AT), and heat flux (HF). The result shows that by increasing the electric field amplitude (EFA) from 1 to 5 V/m, the maximum V and maximum T increase from 0.00086 Å/ps and 240 K to 0.00089 Å/ps and 245 K, respectively. With increasing the external EFA to 5 V/m, the HF value converges to 1395 W/m2, and the AT decreases to 3.90 ns. On the other hand, the change in maximum V in the samples with the pyramid, half-spherical (HS), and rectangular cubic (RC) cavities reached 0.74000 Å/ps, 0.00072 Å/ps, and 0.6565 Å/ps, respectively, and the maximum T changes to 232 K, 238 K, and 235 K in the RC, HS, and pyramid cavities samples. The results show that the structure has a higher HF in the presence of the RC cavity. So, the HF and AT values for samples with RC cavities are 1650 W/m2 and 4.59 ns, respectively.

Conductivity Tensor in Cylindrical Quantum Wire with Parabolic Potential for the Case of Electron-Acoustic Phonon Scattering

Conductivity tensor is an important concept in materials, this work studies conductivity tensors in cylindrical quantum wires with parabolic potential in the presence of two external fields, a linearly polarized electromagnetic wave, and a laser field. This work is also only considered for the case of electron-acoustic phonon scattering. Research results are obtained by using quantum kinetic equations for the carrier system in a quantum wire. The conductivity tensor is calculated by solving the quantum kinetic equation of the system, which is a function of the external field frequency, the external field amplitude, the temperature of the helium, and parameters specific to the quantum wire. Results will also be examined and plotted for quantum wire GaAs / GaAsAl.

Multigrain phase-field simulation in ferroelectrics with phase coexistences: An improved phase-field model

A new 3D phase-field model is developed to investigate the evolution of the domain structure and phase transformation in a ferroelectric material near the morphotropic phase boundary (MPB) under the influence of external stimuli. The model combines the Landau–Ginzburg–Devonshire (LGD) theory with a general multiphase approach and enables to analytically compute the microstructure inside the grain structures with coexisting phases. Together with experimental analysis, a numerical energy overlap was employed to find the phase-dependent phenomenological coefficients. Domain structures and phase transformations in single crystals, as well as in the polycrystalline systems with or without an external electric field have been investigated in a MPB ferroelectric material, by employing phase-field simulation. The simulated results reveal the relation between the polarization switching and the phase transformation under an applied electric field, and the role of the external electric field orientation and amplitude in the domain structure and the phase transformation fraction.

Reversal of domain walls drift direction in a low-frequency magnetic field in iron garnet crystals

The reversal of domain walls (DWs) drift direction in (110) iron garnet plate with shape anisotropy with an increase of the amplitude of an alternating harmonic magnetic field was established experimentally. The harmonic magnetic field H = H0sin(2πft) (f = 3–1000 Hz, H0 up to 2.2⋅104 A/m) was applied perpendicular to the plane of the sample. The DW drift velocities and intensities of nucleation centers of magnetic dislocations (MDs) were measured. It is proposed that the reason for the reversal of direction of the DW drift is a change of direction of the gradient of demagnetizing fields in the sample with an increase of the external field amplitude. The change in configuration of an internal magnetic field is indicated by the experimentally established change in the activity of MD nucleation centers with the increase of the external field amplitude. A model is proposed in which direction and speed of DW drift are determined by magnetic field gradient in the sample.

Nonequilibrium magnetic properties of the Sr2FeMoO6 type double perovskite structure

The Glauber-type stochastic dynamic interpreted by the mean-field theory has been applied to investigate the dynamic magnetic properties of the Sr2FeMoO6 type double perovskite structure under the time varying magnetic field. First, we used the Glauber dynamics to obtain the dynamic mean-field equations. The time varying average Fe and Mo magnetizations are examined to find the phase region of the system. The dynamic Fe and Mo magnetizations, hysteresis loop areas and correlations are calculated depending on the temperature in order to determine the nature of the first and second order phase transitions, as well as to get the dynamic transition points for different ratio of the system parameters. The dynamic phase diagrams (DPDs) are constructed in the plane of reduced temperature and external magnetic field amplitude (T, h). The DPDs contain paramagnetic (p), ferromagnetic (f), ferrimagnetic-1 (i1), ferrimagnetic-2 (i2) phases and six mixed regions, (f + p), (f + i1), (f + i2), (i1 + p), (i2 + p) and (i1 + i2). The DPDs also exhibit dynamic tricritical points and reentrant phenomena, which strongly depend on interaction parameters.

Квантовые свойства диэлектрических потерь в нанометровых слоях твердых диэлектриков при сверхнизких температурах

Using the methods of quasi-classical kinetic theory, continuum electrodynamics, and non-relativistic quantum theory, we construct and study the quantum kinetic equation of proton relaxation, which, together with the Poisson operator equation describes the mechanism of diffusion tunneling transport of hydrogen ions (protons) in the potential field of a crystal lattice perturbed by a polarizing field (quantum diffusion polarization) in crystals with hydrogen bonds. Using the apparatus of the density matrix (statistical matrix), by complete quantum-mechanical averaging of the polarization operator, studies are carried out of the experimental value of the polarization of the dielectric, as a function of the parameters of the external electric field (amplitude, frequency of electromotive force) and temperature. When calculating the equilibrium density matrix for an ensemble of basic relaxers (hydrogen ions), the proton-proton and proton-phonon interactions are not taken into account, and the Hamilton operator for the phonon subsystem is assumed to be a numerical constant for a given crystal under given experimental conditions (calculated by computer method as a parameter for comparing the theory with the experiment). The influence of the phonon subsystem on the kinetics of the relaxation process is reduced to a weak spatially homogeneous force field acting on protons moving in the field of the main forces of hydrogen bonds. The Hamilton of the proton subsystem is constructed for the model of an ideal proton gas in equilibrium with the ionic subsystem of the crystal lattice, and the equilibrium statistical operator of the proton subsystem is written using the Boltzmann quantum statistics. Theoretically, the size effects are found to be manifested in shifts of the low-temperature (50–100 K) maxima of the dielectric loss angle tangent towards ultra-low temperatures (4–25 K) with a decrease in the amplitudes of the maxima by 3-4 orders of magnitude, with a reduction in the thickness of the crystal layer from 1–10 microns to 1–10 nm. The effect of anomalous displacements of low-temperature maxima, which is explained by the abnormally high quantum transparency of the potential barrier for protons (0.8-0.9) in thin films of a crystal with hydrogen bonds (1-10 nm), causes, near the temperatures of the shifted maxima of dielectric losses (4–25 K), a quasi-ferroelectric state, which is also characterized by abnormally high values of the real component of the complete dielectric permittivity (2.5–3.5millions).

Developing highly efficient and electric-field-sensitive fiber-waveguide evanescent couplers.

The slab-coupled optical fiber sensor (SCOS) is an innovative electric field detector with an ultrawide measuring range and a millimeter-level package size. The core sensing part of the SCOS is a fiber-waveguide evanescent coupler (FWEC) that directly determines the device's main performance specifications. This paper presents an investigation of the spectrum characteristics of FWECs with various structural and curing parameters. Methods for fabricating an FWEC with higher resonant depth, narrower free spectral range, and sharper spectrum slope are determined based on the experimental results. Z-cut lithium-niobate FWEC and Z-cut lithium-tantalate FWEC of about ${{1}} \times {0.5} \times {0.3}\;{\rm{mm}}^3$ are fabricated on this basis. Excellent coupling characteristics are achieved in both, according to the relevant spectra. Electric field tests indicate that the peak wavelengths shift linearly with the external AC field amplitude by 0.11 nm/(kV/cm) and 0.24 nm/(kV/cm), respectively. Three optimization methods are proposed to enhance performance: optimizing material selection, adding an antenna structure, and adjusting the calibration method. The results of this work may provide workable guidance for developing miniature, all-dielectric electric field sensors.

Promising magnetic nanoradiosensitizers for combination of tumor hyperthermia and x-ray therapy: Theoretical calculation

Nanoparticle (NP) assisted magnetic hyperthermia (NMH) is a clinically proven method for cancer treatment. High-Z magnetic NPs could also be a perspective object for combining hyperthermia with tumor radiosensitization. However, this application of NPs is little studied, and it is unclear as to what particle compositions one can rely on. Therefore, the present work focuses on the search of materials that combine alternating magnetic field induced heating and high atomic number related dose enhancement abilities. A theoretical evaluation of 24 promising NP compositions was performed: the values of dose enhancement factor (DEF) were determined for kilovoltage x-ray spectra (30–300 kVp), as well as specific absorption rate (SAR) values were calculated for various combinations of elemental compositions and particle size distributions. For the alternating magnetic fields with amplitude 75–200Oe and frequency 100kHz, the maximum obtained SAR values ranged from 0.35 to 6000Wg−1, while DEF values for studied compounds ranged from 1.07 to 1.59. The increase in the monodispersity of NPs led to a higher SAR, confirming well-known experimental data. The four types of SAR dependences on external magnetic field amplitude and anisotropy constant were found for various particle sizes. The most predictable SAR behavior corresponds to larger NPs (∼70–100 nm). Thus, based on these calculations, the most promising for the combination of NMH with radiotherapy, from a physical point of view, are La0.75Sr0.25MnO3, Gd5Si4, SmCo5, and Fe50Rh50. The greatest dose enhancement is expected for superficial radiotherapy (in the voltage range up to ∼60 kVp).

Comparison of Gravitational and Light Frequency Shifts in Rubidium Atomic Clock

The article presents the results of an experimental study of the external magnetic field orientation and magnitude influence on the rubidium atomic clock, simulating the influence of the geomagnetic field on the onboard rubidium atomic clock of navigation satellites. The tensor component value of the atomic clock frequency light shift on the rubidium cell was obtained, and this value was ~2 Hz. The comparability of the relative light shift (~10−9) and the regular gravitational correction (4×10−10) to the frequency of the rubidium atomic clock was shown. The experimental results to determine the orientational shift influence on the rubidium atomic clock frequency were presented. A significant effect on the relative frequency instability of a rubidium atomic clock at a level of 10−12(10−13) for rotating external magnetic field amplitudes of 1.5 A/m and 3 A/m was demonstrated. This magnitude corresponds to the geomagnetic field in the orbit of navigation satellites. The necessity of taking into account various factors (satellite orbit parameters and atomic clock characteristics) is substantiated for correct comparison of corrections to the rubidium onboard atomic clock frequency associated with the Earth’s gravitational field action and the satellite orientation in the geomagnetic field.