Magnetic Field Hc2 Research Articles

Tunable ferromagnetism via in situ strain engineering in single-crystal freestanding SrTiO3-δ membrane

Engineering stoichiometry and lattice field in transition metal oxides (TMOs) is recognized as a promising approach for achieving emergent functional properties and exploring fundamental scientific questions. To overcome the constraints of rigid epitaxial TMOs, this study releases and transfers freestanding SrTiO3-δ (STO3-δ) membranes, derived using a water-dissolution method from STO3-δ/Sr3Al2O6/SrTiO3, onto flexible polyimide. In-plane mechanical strains were then applied to investigate the strain evolution-induced ferromagnetism. Continuous strain modulates interplane and intraplane exchange interactions between neighboring atoms in the ferromagnetic STO3-δ membranes, thereby influencing their ferromagnetic properties. STO3-δ initially undergoes in-plane octahedral distortion when strain is less than 1.5 %, followed by a decrease in the out-plane lattice constant. This structural variation leads to complex strain-dependent behaviors in the saturation magnetic moment (Ms) and coercive field (Hc) of STO3-δ, with Ms and Hc exhibiting a nonlinear, volcano-shaped, and step-wise correlation, respectively. Our research demonstrates that freestanding STO3-δ serves as a platform for studying local defects and their impacts on tunable magnetic properties, greatly enhancing our understanding of t2g electron engineering through modulable inter/intra plane exchange coupling with lattice field.

Investigation of the Magnetic Features of the Fullerene-Dimer-Like Nanostructure (C 60)2: A Monte Carlo Study

The current investigation employs Monte Carlo simulations to explore the magnetic features of a Fullerene-dimer-like nanostructure (C 60)2 characterized by the spin σ−1. It explores how the coupling interaction J σ , the biquadratic parameter K, the external magnetic H and the crystal D fields influence the thermal and magnetic features of the nanostructure, particularly the blocking temperature (T B ). The results also highlight the dependence of hysteresis cycles and the coercive magnetic field Hc on the values of J σ , K, and D, with significant variations at lower temperatures. The findings indicate the distinctive magnetic behavior of the Fullerene-dimer-like nanostructure (C 60)2 potentially useful in various technological applications.

Magnetization spiral structure and high domain wall velocity induced by inertial effect

In ultrafast magnetism, i.e., the short time scales such as picosecond and femtosecond, we report that the spiral structure of magnetization can be formed by the inertial effect. Comparing with the case of fast magnetism in nanosecond time scale, we can obtain a higher velocity of domain wall in ultrafast magnetism due to the driving of inertial moment. There is a critical value τc of angular momentum relaxation time τ for the inertial breakdown in uniaxial ferromagnet. Under the action of the inertial effect the domain wall width shows the characteristics of increases firstly as τ<τc, and then decreasing as τ>τc. It directly leads to the positive or negative mobility for the domain wall velocity as the inertia is less than or exceeds the critical value, respectively. In the high frequency mode (i.e., high field mode), we obtain the limit domain wall velocity, i.e., V→1/ατ. The smaller the inertia or damping, the faster the domain wall moves. For the case of biaxial anisotropic ferromagnets, the domain wall width and velocity decreases with the increasing inertia term, respectively. In the presence of inertia effect, there is an another critical magnetic field hc. The domain wall width decreases with the increase of the magnetic field as h<hc, while increases as h>hc. However, the domain wall velocity shows a nearly linear increase with the magnetic field. These results indicate that the ultrafast magnetism has more advantages than fast magnetism. It also provides a good control technique for rapid information processing in the future.

Facet-dependent magnetic properties of magnetite nanoparticles coated with dodecyl amine and their biological effect in hepatocarcinoma cell line

Herein was conducted a compelling structural analysis of magnetite nanoparticles (NPs) coated with dodecyl amine (DDA), compared with uncoated magnetite, both previously synthesized by an accelerated one-pot synthesis, starting from a single iron precursor. XRD/TEM results for the obtained nanomaterial Fe3O4@DDA showed the predominance of Fe3+ cations on the most stable atomic plane of magnetite (111). Using Molecular Dynamics calculations, with the observed atomic dispositions as inputs, it was established that NPs' surface and DDA might interact by short-distance coordination, with DDA as a ligand of Fe3+ cations, or by long-distance adsorption via H-bonding. The simulations align with TEM images, revealing an amorphous contour corresponding to the organic coating arranged as a bilayer. The TGA analysis corroborated a dual mass loss profile relating to the DDA bilayer at 116 °C and 350 °C. The Fe3O4@DDA NPs’ magnetic properties (saturation magnetization (Ms) and coercivity field (Hc)) were preserved. Fe3O4@DDA exhibited a reduction of 3 emu/g in Ms and an increment of 12 Oe in Hc, compared with Fe3O4 NPs, attributable to the coating inhomogeneity and the consequent anisotropy rise. Fe3O4@DDA triggered concentration-dependent cytotoxic effects on the human hepatocarcinoma cell line HepG2. At 50 µg/mL after incubation of 48 h, cell viability was 63% < , whereas at 72 h only 30% of cells were viable. At 300 µg/mL, less than 10% of HepG2 cells remained viable after 24 h of incubation. In the case of Fe3O4 NPs assessed in the same cell line, cell viability remained as high as 80% at 300 µg/mL during 72 h of incubation. Trypan blue assay suggests membrane integrity damage as the primary mechanism of HepG2 cell death. Even though the in vitro results herein presented are preliminary, they represent the first report of the cytotoxic effect of magnetite coated with a nitrogenous surfactant.Graphical abstract

Magnetization Plateaus of a Double Fullerene Core/Shell Like-Nanostructure in an External Magnetic Field: Monte Carlo Study

Abstract: This paper concerns the investigation of the critical (HC) and the saturation (HS) magnetic fields behavior of the studied system as a function of different physical parameters. The Monte Carlo method is used to study the magnetic properties of the ferrimagnetic behavior of a double fullerene X60 core/shell-like nanostructure. Based on the Ising model, we focus our study on a system formed by a double sphere core/shell. The two spheres contain the spins  = ± 1/2 in the core surrounded by the spin S = ± 1, 0 in the shell. Various types of magnetization curves have been established, depending on the competition among the exchange couplings, the crystal fields, and the temperature. The study reveals that the saturation magnetic field (Hs) is significantly influenced by variations in all exchange coupling parameters, whereas the critical magnetic field (Hc) is only mildly affected by these parameter variations. Moreover, the crystal field and temperature both influence the critical and saturation magnetic fields. Keywords: Double fullerene core/shell-like structure, Magnetization plateaus, Monte Carlo simulations, Critical and saturation fields, External magnetic field.

THE STUDY ON TEMPERATURE-DEPENDENT SURFACE CRITICAL MAGNETIC FIELD OF IRON-BASED SUPERCONDUCTORS

The upper critical magnetic field (Hc2) is one of the important properties of superconductors in external magnetic field. The higher magnetic field strength, the more superconductivity is maintained. However, the surface critical magnetic field (Hc3) is larger than upper critical magnetic field which the ratio of Hc3 to Hc2 is constant. In this study, we investigated the surface critical magnetic field of the iron-based superconductor using Ginzburg-Landau’s anisotropic two-band method. The surface critical magnetic field was calculated with four temperature-dependent models. Our analytical formula of the surface critical magnetic field obtains the temperature parameters. Finally, the numerical calculation was applied to the experimental data of iron-based superconductors

Giant room-temperature modulation of magnetic anisotropy by electric fields in CoFeB/(011)-PMN-PT multiferroic heterostructures with two distinct initial magnetic anisotropies

This paper reports that the in situ growth magnetic field (Hg) during magnetic-phase CoFeB deposition impacts the electric-field control of magnetic anisotropy in Co40Fe40B20/(011)-Pb(Mg1/3Nb2/3)0.7Ti0.3O3 [CoFeB/(011)-PMN-PT] composite multiferroic heterostructures at room temperature. In the Hg1 mode (in situ Hg along the [011¯] direction of the ferroelectric PMN-PT substrate), the electric-field-controlled modulation ratios of the magnetic coercivity HC and saturation magnetic field HS are approximately −47% and +156%, respectively. However, in the Hg2 mode (in situ Hg along the [100] direction of the ferroelectric PMN-PT substrate) of the CoFeB/(011)-PMN-PT multiferroic heterostructure, the electric-field-controlled modulation ratios of the magnetic coercivity HC and saturation magnetic field HS can reach as high as +162% and +393%, respectively. Moreover, the electric-field-controlled magnetic coercive field HC exhibits a butterfly shape when plotted versus the applied electric fields in both modes, which matches the in-plane butterfly strain loop of the ferroelectric PMN-PT substrate. However, the electric-field-controlled saturation magnetic field HS presents a square loop, which is very consistent with the ferroelectric loop of the PMN-PT substrate. This result may be ascribed to the distinct pathway of the ferroelastic domain switching in the (011)-oriented PMN-PT substrate. This study provides a new idea for the design of spintronic devices based on multiferroic heterostructures.

Investigation of the structural, electrical and magnetic properties of vanadium substituted Mn–Zn ferrites

This work revealed the role of altering vanadium (V) content in Mn–Zn ferrites. We used the traditional solid-state reaction method to prepare the {mathrm{Mn}}_{0.5}{mathrm{Zn}}_{0.5}{mathrm{V}}_{mathrm{x}}{mathrm{Fe}}_{2-mathrm{x}}{mathrm{O}}_{4} (x = 0.0, 0.05, 0.10, 0.15, 0.20) ferrites. Powder X-ray diffraction was used to analyze the samples’ crystal structures, revealing the prepared sample’s spinal cubic crystal structure. With increasing Vanadium concentration, the lattice constant drops proportionately. We used Debye–Scherrer (D–S), Williamson–Hall (W–H) Plot, Halder–Wagner (H–W) Langford, and Size Strain Plot (SSP) methods to compare different structural properties. We also used the impedance analyzer to investigate the samples’ dielectric characteristics and AC conductivity at room temperature over a frequency range of 1 kHz–100 MHz. The magnetic properties, i.e., Saturation magnetization (Ms), Coercive field (Hc), and Remanent magnetization (Mr), were estimated from the ferromagnetic hysteresis behavior of the samples measured using a vibrating sample magnetometer (VSM). The saturation magnetization was observed to decrease with an increase in V content. The Mr and HC vary non-linearly with V contents. The prepared samples’ initial permeability was tested, and a reasonably constant complex permeability (µ') was recorded over a wide frequency range (~ 1000 Hz).

Robust superconductivity and huge enhancement of upper critical field in Nb2CS2 MXene under high pressure

As a member of the emerging MXenes family, Nb2CS2 offers distinctive superconductivity, excellent electrical properties, and outstanding chemical stability, making it potentially useful for energy storage, medical imaging, and quantum computing. Herein, we systematically investigate how ultrahigh pressure affects the electrical properties of Nb2CS2. The results indicate that Nb2CS2 retains robust superconductivity with Tc&amp;gt;8 K up to the maximum applied pressure of 146.8 GPa. Moreover, the upper critical magnetic field Hc2(0) of Nb2CS2 increases with pressure, and the Pauli limit is violated at pressures greater than 120 GPa. Meanwhile, Hc2(0) increases to 19.3 T at 146.8 GPa, which is 4.8 times greater than at the initial pressure. Further analysis suggests that the significant enhancement of Hc2(0) below 30 GPa comes from the sharp pressure-induced rise of carrier concentration as the interlayer distance decreases, and the significant increase in Hc2(0) above 86 GPa may come from enhanced spin–orbit coupling or the possible unconventional superconducting pairing mechanisms. These results provide insights into the superconducting properties of MXene materials and offer guidelines for further research on electronic transport in Mxenes under ultrahigh pressure.

Large room-temperature magnetodielectric effect in polyvinylidene fluoride-trifluoroethylene/La0.7Sr0.3MnO[formula omitted] (0-3) nanocomposite thin films

We observe large room-temperature magnetodielectric effect (nearly 12% suppression of dielectric constant under ∼20 kOe field) as well as its remarkable field-driven switch – from positive to negative – in polyvinylidene fluoride-trifluoroethylene/La0.7Sr0.3MnO3 (PVDF-TrFE/LSMO) thin films (0–3 connectivity) containing 7.5 volume% LSMO. The magnetodielectric effect is mapped with the volume fraction of the LSMO nanoparticle across 5-20 volume%. It reveals a close correlation among the LSMO nanoparticles volume fraction, their distribution pattern within the PVDF-TrFE matrix, uniformity in the magnetic domain size (imaged by magnetic force microscopy), and the magnetodielectric effect. The observed 20% jump in the intrinsic bulk capacitance at a critical magnetic field HC∼10 kOe can be exploited to develop smart nanoscale magnetoelectric devices.

PANI-coated YIG/CFO hybrid composites as advanced electromagnetic wave absorber through X-band

Polyaniline (PANI)-coated Y3Fe5O12(YIG)/CoFe2O4(CFO) hybrid composites were synthesized via sol-gel and oxidative polymerization methods to achieve advanced microwave absorption properties. The structural, morphological, magnetic, and microwave absorption characteristics of the resulting samples were analyzed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration sample magnetometer (VSM), and vector network analyzer (VNA). XRD results revealed that CFO and YIG have cubic crystal structures with Fd3m and Ia3d space symmetry, respectively, with an average crystallite size of 35.3 nm and 42.9 nm. The Ferro/ferrimagnetic signals were detected from the ferrite samples' room temperature magnetic hysteresis loops. The incorporation of PANI and YIG into the composites resulted in a decrease in their magnetic saturation (Ms) and coercive field (Hc) values. VNA measurements demonstrated that nearly all samples achieved 90% absorption (≤−10 dB) of incident electromagnetic waves throughout the X-band frequency range. The minimum reflection loss (RLmin) value reaches − 47.34 dB at 8.14 GHz, with an effective bandwidth of 4.00 GHz, covering the entire X-band and beyond. These impressive absorption characteristics suggest that the manufactured composites possess potential as viable candidates for defense applications conducted at X-band frequency.

Search for superconductivity in hydrides of TiZrNb, TiZrNbHf and TiZrNbHfTa equimolar alloys

We have prepared and investigated the superconducting equimolar alloys TiZrNb, TiZrNbHf and TiZrNbHfTa, which exhibit transition temperatures Tc between 6.4 K and 8.4 K, and examined the influence of hydrogenation on their superconductivity. The upper critical magnetic field Hc2 of alloys was estimated to be above 10 T, in agreement with previous studies of superconducting alloys of similar composition. On the other hand, the hydrogenation of alloys, some of which appear to be promising for hydrogen storage, lead to suppression of superconductivity in TiZrNb, TiZrNbHf and TiZrNbHfTa dihydrides and in TiZrNbHfTa monohydride, and no transition to superconducting state was observed therein above 2 K. A possible reason for this may be related to the high concentration of disorder (defects) in hydrides originating from the preparation method during which the starting alloy disintegrates into fine powder.

Effect of Magnetic Impurities on Superconductivity in LaH10.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications. On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH10 , encounters a serious complication because of the large upper critical magnetic field HC2 (0), exceeding 120-160T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH10 : each at% of Nd causes a decrease in TC by 10-11K, helping to control the critical parameters of this compound. Strong pulsed magnetic fields up to 68T are used to study the Hall effect, magnetoresistance, and the magnetic phase diagram of ternary metal polyhydrides for the first time. Surprisingly, (La,Nd)H10 demonstrates completely linear HC2 (T)∝|T -TC |, which calls into question the applicability of the Werthamer-Helfand-Hohenberg model for polyhydrides. The suppression of superconductivity in LaH10 by magnetic Nd atoms and the robustness of TC with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson's theorem gives new experimental evidence of the isotropic (s-wave) character of conventional electron-phonon pairing in lanthanum decahydride.

Aluminum-titanium-cobalt substituted epsilon iron oxide nanosize hard magnetic ferrite for magnetic recording and millimeter wave absorption

We synthesized aluminum-titanium-cobalt substituted epsilon iron oxide (ATC-ε-Fe2O3), ε-Al0.11Ti0.04Co0.05Fe1.80O3 (1), ε-Al0.14Ti0.04Co0.05Fe1.77O3 (2), and ε-Al0.26Ti0.04Co0.05Fe1.65O3 (3). The magnetic coercive field (Hc) values are 7.1 kOe (1), 6.5 kOe (2), and 4.4 kOe (3). Zero-field ferromagnetic resonance frequencies (fr) were observed at 112 GHz (1), 109 GHz (2), and 100 GHz (3) using terahertz time-domain spectroscopy. These Hc and fr values are suitable for high-density magnetic recording and high-frequency millimeter wave absorbers. Additionally, the present series is non-toxic, low-cost, and could be used as practical magnetic fillers for magnetic recording and millimeter wave absorber applications.

Wide modulation of coercive fields in Mn4N ferrimagnetic thin films caused dominantly by dislocation microstructures

Perpendicular magnetic anisotropy and coercive fields (Hc) are governed by the degree of order of N (S) in ferrimagnetic Mn4N thin films. However, in this study, we observed non-negligible modulation of Hc extending from 10 to 7.5 kOe for three Mn4N films grown at a substrate temperature (Tsub) in the range of 400–500 °C, even with identical S, which has not been discussed to date. The possible mechanisms for this phenomenon were explored by transport properties and fine structural analysis. The results indicated that longitudinal resistivity and anomalous Hall resistivity remain unchanged for three Mn4N films. Conversely, the number of dislocations and in-plane grain size (D) increased, whereas the residual strain (ε) decreased with increasing Tsub. This indicates that Hc of the Mn4N film with the same S is sensitive to the variation in dislocations, D and ε. Tunable Hc of this type can be effectively applied in magnetic and spintronic devices using ferrimagnetic Mn4N films, because Hc is an important determinant of the thermal stability of magnetization and working power consumption.

Effect of the thickness of BiFeO3 layers on the magnetic properties of BiFeO3/La2/3Sr1/3MnO3 heterostructures

BiFeO3 (BFO) thin films with different thicknesses were deposited on La0.67Sr0.33MnO3 (LSMO) buffered SrTiO3 (001) substrate using a pulsed laser deposition technique. The variation in the out-of-plane lattice parameter and magnetic properties of BFO/LSMO with various thicknesses of BFO are explored. The lattice parameter of BFO decreases with the increasing thickness of BFO and approaches to a value corresponding to bulk BFO. The remanent magnetization (Mr) and magnetic coercive field (Hc) of BFO/LSMO heterostructures depend on the thickness of the top layer BFO. The maximum values of Mr and HC in BFO/LSMO are observed for BFO with thickness (tBFO) equal to ∼25 nm. For tBFO > 25 nm, both Mr and Hc of BFO/LSMO decrease with increasing thickness of the BFO layer. Further, a wasp-waisted shape in the M-H loop of BFO/LSMO perceptible at a high temperature (100 K) may be originated from a new magnetic phase in the BFO layer at the interface due to Fe3+ and Mn3+/4+ magnetic interactions between the two layers. The exponential decay of the HC(T) with increasing temperature suggests the multiple competing interactions, such as Fe3+-O-Fe3+ and Fe3+-O-Mn3+/4+ and Mn3+/4+ -O-Mn3+/4+ leading to a spin-glass state in the interfacial region. The variations in the magnetic properties of BFO/LSMO with the thickness of BFO may be associated with the single domain to multi-domain transition and/or linked to the effect of the epitaxial strain, and Fe3+ and Mn3+/4+ magnetic interactions in the vicinity of the interface.

Study of RHQT-processed Nb3Al multifilamentary rectangular tape strand to be applied to a fusion magnet

Nb3Al superconducting wire shows an excellent strain tolerance compared with Nb3Sn wire and is promising conductor for a future fusion magnet. We investigated about the changes of the superconducting property and the wire flexibility by rectangular tape-shaped deformation on the Rapid Heating/Quenching and Transformation (RHQT) processed Nb3Al multifilamenatry wires. The improvement of the wire flexibility will be enable to the future complicated coil winding through the "React and Winding" process. The Rapid Heating/Quenching (RHQ) treatment was performed on a round-shaped Nb/Al precursor wire, and Nb/Al filaments has converted to the ductile bcc Nb-Al supersaturated solid solution (bcc-SS) phase after the RHQ (Rapid heating and quenching) treatment. The round-shaped wire after the RHQ treatment could be easily cold flat-rolled to the rectangular tape-shape (width: 4.6 mm, thickness: 0.2 mm) at room temperature. The phase transformation from bcc-SS phase to stoichiometric A15-Nb3Al phase by the post-annealing was confirmed. Critical current (Ic) and critical current density (Jc) at 4.2 K and 18 T of the RHQT processed Nb3Al rectangular tape strand was obtained approximately 180 A and 200 A/mm2, respectively. Jc property above 18 T in the rectangular tape strand were clearly improved compared to the round wire strand, and the upper critical magnetic field (Hc2) above 26 T was also obtained. In addition, no Ic deterioration by applying a bending strain up to 0.66% was observed. The wire flexibility of the RHQT processed Nb3Al strand could be improved by the change of wire shape from round wire to rectangular tape. We found that the Nb3Al rectangular tape stand will be desirable and suitable material to apply to a future huge fusion magnet through the React & Winding process.

Enhancement of critical current density and strong vortex pinning in high entropy alloy superconductor Ta[formula omitted]Nb[formula omitted]Hf[formula omitted]Zr[formula omitted]Ti[formula omitted] synthesized by spark plasma sintering

We synthesized the high entropy alloy (HEA) Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 compound by planetary ball milling and the spark plasma sintering (SPS) method. The sintered HEA sample had a BCC crystal structure with small amount of secondary phases. The superconducting phase transition is observed in the electrical resistivity (Tc∼ 7.8 K) and magnetic susceptibility (Tc∼ 7.6 K) measurements, and the Tc was similar to that of an arc-melted sample. The zero-temperature limit of the upper critical magnetic fields Hc2(0)= 10.5 T and coherence length ξ = 5.66 nm were slightly decreased or comparable to the arc-melted HEA sample (Hc2(0)= 12.05 T and ξ= 5.23 nm). The field-dependent isothermal magnetization hysteresis M(H) exhibited the typical type- 2 superconducting behavior with magnetic flux avalanches in the low magnetic field region. The calculated critical current densities were significantly increased by 286 % (Jc= 32,606 A cm−2 at 2 K) ∼ 687 % (Jc= 73,200 A cm−2 at 4 K) compared to the arc-melted HEA sample (Jc= 11,401 A cm−2 at T= 2 K). The enhanced Jc of the sintered HEA sample is caused by enhancement of the pinning force due to point pinning as well as surface pinning effects. The vortex relaxation measurements showed stable remanent magnetization for over 10,000 s after magnetic fields were turned off, which is unlike conventional sueprconducting vortex relaxation behavior. The strong pinning force in the SPS sintered Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 compound is beneficial for practical applications because of the significantly enhanced critical current density Jc with stable remanent magnetization Mrem(t).

Role of Y substitution for Ca-site on magneto-resistivity properties of Bi-2212 superconductor rods prepared by LFZ

This comprehensive study delves into the effect of partial Y3+ substitution for Ca2+ in Bi2Sr2CaCu2O8+y superconducting rods prepared by the laser floating zone method (LFZ). The critical transition temperatures (Tconset, Tc, Tcoffset), activation energy (U), irreversibility field (Hirr), upper critical magnetic field (Hc2), coherence length (ξ), and penetration depth (λ) are determined by means of magneto-resistivity measurements performed between 0 and 5 T. According to the resistivity-temperature graph for zero fields, Tcoffset values tend to decrease regularly from 90.8 K to 87.1 K, and the residual resistivity values increase steadily from 0.14 to 9.7 mΩ .cm with the Y-content. The change of these two parameters is a sign that Y-introduction into the Bi-2212 matrix undermines the inter-grain coupling and increases the level of permanent-defects in the crystalline structure. However, the relatively high Tcoffset values and extremely low residual resistivity, especially in the pure and low Y-substituted samples, reflect the success of the LFZ process in growing homogeneous and well-oriented Bi-2212 grains. The resistivity transition broadening is observed when the applied field increases and Tcoffset values decrease dramatically, i.e. from 90.8 K to 72.1 K for the pure sample and from 87.1 K to 48.2 K for the 0.20Y-substituted ones. The calculated U values using the TAFF model decrease with the increase of the Y-content and the magnetic field. In addition, the magnetic field and temperature dependence of U is expressed by using U(H,T) ∼ ΔT H−η equation. Deduced parameters of Hirr and Hc2 from magneto-resistivity curves and theoretical findings of ξ and λ also favor the degradation of U values with the augmentation of Y-content in the Bi-2212 rods.

Effect of mechanical milling on magnetic, dielectric and magneto-electric properties of Z- type (Ba, Sr) hexaferrites

The Z-type hexaferrites Sr3Co2Fe24O41 (SCFO) and Ba3Co2Fe24O41 (BCFO) were prepared via sol-gel method and were ball milled for different duration to study the effects of reduction in particle on the physical properties of these compounds. The phase formation was confirmed by using X-ray diffraction (XRD) whereas Scanning Electron Microscopy (SEM) was employed to analyze the surface morphologies of these samples. Magnetization measurements i.e. (M-H) at room temperature were performed by using Vibrating Sample Magnetometer (VSM) and it is observed that the magnetic coercive field (Hc) has increased with reduction in particle of the samples i.e., with ball milling. Magneto electric effects of (Ba, Sr) Z-type hexaferrites at room temperature were measured indirectly by examining the change in polarization (P-E loop) with and without magnetic field. It is evident from P-E loops of SCFO that magnetic field affects the electric polarization for all ball-milled samples and it is an indication of ME coupling in these samples at room temperature.