scholarly journals Structural, Magnetic and Microwave Characterization of Polycrystalline Z-Type Sr3Co2Fe24O41 Hexaferrite

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2355
Author(s):  
Svetoslav Kolev ◽  
Petya Peneva ◽  
Kiril Krezhov ◽  
Tanya Malakova ◽  
Chavdar Ghelev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Sol Gel ◽  
Peak Frequency ◽  
Magnetic Phase Transitions ◽  
Microwave Properties ◽  
Zero Field ◽  
Auto Combustion ◽  
Dramatic Rise ◽  
Absorbing Material

We report results on the structural and microwave properties and magnetic phase transitions in polycrystalline Sr3Co2Fe24O41 hexaferrite synthesized by sol-gel auto-combustion and acting as a filler in a composite microwave absorbing material. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves revealed a change in the magnetization behavior at 293 K. The reflection losses in the 1–20 GHz range of the Sr3Co2Fe24O41 powder dispersed homogeneously in a polymer matrix of silicon rubber were investigated in both the absence and presence of a magnetic field. In the latter case, a dramatic rise in the attenuation was observed. The microwave reflection losses reached the maximum value of 32.63 dB at 17.29 GHz in the Ku-band. The sensitivity of the microwave properties of the composite material to the external magnetic field was manifested by the appearance of new reflection losses maxima. At a fixed thickness tm of the composite, the attenuation peak frequency can be adjusted to a certain value either by changing the filling density or by applying an external magnetic field.

scholarly journals Coherent emission from the stack of Josephson junctions with the non-uniform inductive interaction

2019 ◽  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Gaussian Distribution ◽  
Josephson Junctions ◽  
Critical Currents ◽  
Collective Modes ◽  
Zero Field ◽  
Strong Emission ◽  
Inductive Interaction ◽  
Coherent Emission

During last decade, considerable efforts were made to achieve coherent emission from stacks of many Josephson junctions. It is known that strong emission from a junction in the presence of external magnetic field appears at the so-called Fiske steps in the IV-characteristic at voltages which correspond to frequencies of geometrical resonances. However, it is possible to obtain resonant steps in long junctions without external magnetic field. The periodical movement of fluxons is excited due to some disorder in the distribution of critical currents along junctions. The so-called zero-field steps are formed in the IV-curve due to the interaction of fluxons with oscillations of voltage at Josephson frequencies. We investigated numerically IV-characteristics and the dependence of the average square of ac voltage at the end of the stack of two long Josephson junctions on the average voltage. Junctions interacted inductively with each other. We introduced not only the Gaussian distribution of critical currents along junctions but also the Gaussian distribution of coefficients of the interaction between junctions (mutual inductances). Zero-field steps in the IV-characteristic were found at voltages which corresponded to frequencies of in-phase collective modes in the stack as well as to frequencies of uncoupled junctions. Zero-field steps appeared in the hysteretic region of the IV-curve. There appeared also jumps of voltage from the resistive branch to the zero-field step. We showed that there existed distributions of mutual inductances along junctions which provided jumps to voltages at which the average square of ac voltage at the end of the stack (which is proportional to power of emission) was larger than that for the stack with the uniform distribution of mutual inductances.

scholarly journals Self-standing magnetic composite nanosheets prepared in the presence of an external magnetic field: Characterization and potential for medical applications

2020 ◽  
pp. 174751982095860
Author(s):  
Mina Sakuragi ◽  
Yoshikazu Takahashi ◽  
Keito Ehara ◽  
Katsuki Kusakabe
Keyword(s):  
Magnetic Field ◽  
Thermal Decomposition ◽  
External Magnetic Field ◽  
Decomposition Method ◽  
Sol Gel ◽  
Magnetic Composite ◽  
Magnetic Response ◽  
Gel Method ◽  
Sol Gel Method ◽  
Thermal Decomposition Method

The aim of this study is to develop self-standing, ultrathin film, nanosheets with high magnetic response for use in a medical device that can be migrated to a target location in the body by using an external magnetic field. First, iron oxide nanoparticles are synthesized by either the sol-gel method or thermal decomposition. The resulting magnetic properties of the nanoparticles show that the thermal decomposition method provides a greater saturation magnetization value than the sol-gel method. Next, the nanoparticles obtained by the thermal decomposition method are embedded into nanosheets of poly(L-lactide) at varying concentrations. Embedding of the nanoparticles in the composite nanosheets is achieved by the application of an external magnetic field. The composite nanosheets are then characterized. The thickness of the nanosheet increases, and the nanoparticles are well dispersed, with an increase in poly (L-lactide) concentration. The NP-embedded nanosheets are imaged by transmission electron microscopy, which reveals thin, long aggregates aligned in collinear line features. X-ray diffraction results indicate that the magnetic hard axis of the nanoparticles in the nanosheets is aligned in parallel to the plane of the nanosheet by magnetic field application during nanosheet preparation. In addition, the nanosheets at high poly (L-lactide) concentrations that had been subjected to a magnetic field during preparation show a slightly greater magnetic response compared with both nanosheets without magnetic field exposure and nanosheets prepared at low poly (L-lactide) concentrations.

scholarly journals Microwave Properties of Ferromagnetic Nanowires and Applications to Tunable Devices

2009 ◽  
Vol 152-153 ◽  
pp. 389-393 ◽  
Author(s):  
Judith Spiegel ◽  
Isabelle Huynen
Keyword(s):  
Magnetic Field ◽  
Dielectric Properties ◽  
External Magnetic Field ◽  
Filling Factor ◽  
Microwave Properties ◽  
Microwave Devices ◽  
Microwave Circuit ◽  
Broad Bandwidth ◽  
Ferromagnetic Nature ◽  
The One

Microwave devices as circulators or tunable filters demand nowadays small size and broad bandwidth. Ferromagnetic nanowired membranes are ideal candidates for this purpose. This paper focuses on the dielectric properties of such substrates, as influenced by the ferromagnetic nature of nanowires and their filling factor. Two particular cases are considered: a membrane filled up to its top with nanowires, forming a one-layer substrate, and a membrane filled up to a certain percentage of its height with nanowires, forming a two-layer substrate. The models proposed in this paper for each case take the inductive and gyromagnetic effects in the wires into account. They predict for the one-layer case a magnetodielectric behavior which is tunable by applying an external magnetic field. The effect is no longer visible for the two-layer topology corresponding to microwave circuit applications.

Spectral selectivity of 3D magnetophotonic crystal film fabricated from single butterfly wing scales

Nanoscale ◽  
2014 ◽  
Vol 6 (11) ◽  
pp. 6133-6140 ◽  
Author(s):  
Wenhong Peng ◽  
Shenmin Zhu ◽  
Wang Zhang ◽  
Qingqing Yang ◽  
Di Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Sol Gel ◽  
Butterfly Wing ◽  
Spectral Selectivity ◽  
Crystal Film ◽  
Sol Gel Process ◽  
Magnetophotonic Crystal ◽  
Wing Scales ◽  
Magnetite Film

A magnetite film with photonic structures, which possess spatial optical anisotropy properties and can be tuned by an external magnetic field, has been successfully fabricated by a simple sol–gel process.

Magnetic Prehistory in the Heat Capacity of the Low-Temperature Superconductors

2015 ◽  
Vol 233-234 ◽  
pp. 741-744
Author(s):  
Sergey Mikhailovich Podgornykh
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
External Magnetic Field ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Ring Specimen ◽  
Trapped Flux ◽  
The Magnetic Field

Effect of the magnetic prehistory on the temperature dependence of the heat capacity of the superconducting Pb, La, Sn. has been studied. As soon as the external magnetic field riches the valueHext=HCthe superconductivity is completely destroyed. The trapped flux was produced in the ring specimen after the magnetic field was turned off atT<TC. We observed a difference of the value of the heat capacity between zero field cooled (ZFC) and field cooled (FC) states in zero magnetic field for the ring specimen. It is found that the FC heat capacity is smaller than the heat capacity both in the normal and in superconducting states.

STABILITY OF SKYRMIONS IN THE FRUSTRATED ANTIFERROMAGNETIC/FERROELECTRIC BILAYERS WITH THE TRIANGULAR LATTICE

2021 ◽  
Vol 0 (1) ◽  
pp. 17-22
Author(s):  
I.F. SHARAFULLIN ◽  
◽  
A.R. YULDASHEVA ◽  
N.M. NUGAEVA ◽  
H.T. DIEP ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Triangular Lattice ◽  
Ground State ◽  
Steepest Descent Method ◽  
Magnetic Phase Transitions ◽  
Magnetoelectric Interaction ◽  
Spin Configuration ◽  
Ferroelectric Layer ◽  
Antiferromagnetic Layer

The formation and conditions of stability of a skyrmions at the interface between a ferroelectric layer and antiferromagnetic layer with triangilar lattice and its phase transition are studied. All interactions between spins and polarizations are limited to nearest neighbors (NN). The antiferromagnetic exchange interaction among the spins inside antiferromagnetic layer will compete with the perpendicular interface interaction between adjacent layers. The ground state spin configuration at zero temperature is calculated by using the numerical high performance steepest descent method. The resulting configuration is non-collinear. Small values of external field yields small values of angles between spins in the plane so that the ground state configurations have antiferromagnetic and non collinear domains. We observe the creation of single spin vortices. We noted that for zero applied magnetic field the skyrmions in the antiferromagnetic/ferroelectric bilayers with triangular lattice can be created in the region of interface magnetoelectric interaction value between 0.85 and 1.95. The strong external magnetic field applied perpendicular to the interface with non-collinear Dzyaloshinskiy-Morya-like magnetoelectric interaction at the interface leads to remove the skyrmion phase and magnetic phase transitions. With increasing the interface magnetoelectric coupling, the skyrmion lattice disappear. We found the formation perfect skyrmion structure at non-zero external magnetic field and moderate values of magnetoelectric interaction. The skyrmions structure is stable in a large region of the interface magnetoelectric interaction between antiferromagnetic and ferroelectric films. The results of Monte Carlo simulations that we carried out confirm that observed skyrmions are stable up to a finite temperature.

Rotational structure of triplet–singlet transitions in orthorhombic molecules in intermediate and high magnetic fields

1977 ◽  
Vol 55 (12) ◽  
pp. 1066-1073 ◽  
Author(s):  
C. di Lauro ◽  
E. Perri
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
External Field ◽  
Triplet State ◽  
Rotational Structure ◽  
High Magnetic Fields ◽  
Zero Field ◽  
High Fields

The Zeeman band profiles are calculated for near-case (b) triplet–singlet transitions in asymmetric rotors, making allowance for the intensity perturbations induced by an external magnetic field. It is shown that new bands correlating with zero-field forbidden lines can be observed under the effect of sufficiently high fields. Band profiles and the patterns of the magnetic sublevels of the triplet state split by the external field are discussed in detail for the Paschen–Back limit.

Soft matter, sol–gel process and external magnetic field to design macrocellular silica scaffolds

2005 ◽  
Vol 263 (1-3) ◽  
pp. 341-346 ◽  
Author(s):  
Florent Carn ◽  
Annie Colin ◽  
Véronique Schmitt ◽  
Fernando Leal Calderon ◽  
Rénal Backov
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Soft Matter ◽  
Sol Gel ◽  
Sol Gel Process

Positive zero-field splitting and unexpected slow magnetic relaxation in the magneto-chemical calibrant HgCo(NCS)4

2021 ◽  
Vol 50 (10) ◽  
pp. 3468-3472
Author(s):  
Roman Boča ◽  
Ján Titiš ◽  
Cyril Rajnák ◽  
J. Krzystek
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Relaxation ◽  
Positive Zero ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Slow Magnetic Relaxation ◽  
Splitting Parameter

Magnetochemical standard HgCo(NCS)4 with positive zero-field splitting parameter D displays a slow magnetic relaxation strongly dependent upon the external magnetic field.

Asymptotic inference for an Ising lattice III. Non-zero field and ferromagnetic states

1979 ◽  
Vol 16 (1) ◽  
pp. 12-24 ◽  
Author(s):  
David K. Pickard
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Statistical Inference ◽  
Central Limit ◽  
Spatial Interaction ◽  
Zero Field ◽  
Nearest Neighbour ◽  
Ising Lattice ◽  
Asymptotic Inference ◽  
Limit Result

In previous papers (1976), (1977) limit theorems were obtained for the classical Ising model in the absence of an external magnetic field, thereby providing a basis for asymptotic inference. The present paper extends these results to arbitrary external magnetic fields. Statistical inference for this model is important because its nearest-neighbour interactions provide a natural first approximation to spatial interaction among binary variables located on square lattices.The most interesting behaviour occurs in zero field and at or beyond the critical point. In this case, the central limit result for nearest-neighbour interactions requires an unusual norming, the limiting variances may depend on the nature of the boundary conditions, and there cannot be any central limit result for external magnetic field. The implications of these phenomena for statistical inference are also discussed. In particular, the maximum likelihood estimator of magnetic field is not consistent. Rather it appears to have a non-trivial asymptotic distribution.

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