Oe Field Research Articles

Study of magnetocaloric properties of small Bi-doped Pr0.55Ca0.05Ba0.40Mn1−xBixO3 manganites

Here, we investigated the magnetic and magnetocaloric (MC) properties of manganites labeled PrCaBaMnO and PrCaBaMnBiO, with compositions Pr0.55Ca0.05Ba0.40Mn1−xBixO3 (x = 0 and 0.02), respectively. The solid-state reaction method was used for sample preparation, and the structural properties were checked using X-ray diffraction (XRD). Temperature dependence of magnetization (M(T)) measurements was carried out in the range of 5–300 K under 100 Oe field to determine the transition temperature of the manganites. Magnetic entropy change (-ΔSM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{\ ext{M}}$$\\end{document}) values were computed from field-dependent magnetization (M(H)) measurements. For the 2 T magnetic field values, the -ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {{S}_{ }}_{\ ext{M}}^{\ ext{max}}$$\\end{document} values for the PrCaBaMnO and PrCaBaMnBiO manganites are 3.15 and 2.86 Jkg-1K-1, respectively. Relative Cooling Power (RCP) values were calculated from the temperature dependence of -ΔSM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{\ ext{M}}$$\\end{document} (T) curves, resulting in 82.4 and 88.6 Jkg-1 for PrCaBaMnO and PrCaBaMnBiO, respectively. Banerjee’s criterion and Franco’s universal master curve confirmed that the transition type for the studied manganites is second order.

Investigation of optical and magnetic properties of 3d-4d transition metal ion based double Perovskite: Sr2MnRuO6

Investigation of physical properties in double perovskites, A2B′B″O6, containing 3d/4d transition metal ions at the B sites is an interesting avenue of research. In this study, we focus on Sr2MnRuO6, exploring its structural, morphological, optical and magnetic properties. Sr2MnRuO6 was synthesized in single phase using solid-state reaction route. It crystallizes in a tetragonal structure (space group I4/mcm, #140) with lattice parameters a = 5.4633 (2) Å, c = 7.9419 (1) Å. X-ray diffraction analysis revealed no super lattice reflections, indicating disorder in the B-site cations.The Jahn-Teller distortion in Mn-O6 octahedra,as revealed by XRD results, indicates a high spin state for the Mn3+ ion. The stoichiometric ratio of Sr: Mn: Ru (∼2:1:1), as determined by bond valence sum calculations and confirmed by energy dispersive x-ray spectroscopy agree well with the nominal composition of Sr2MnRuO6. Diffuse reflectance spectroscopy showed strong absorption throughout the visible region with a direct band gap of ∼3 eV, indicating Sr2MnRuO6 is a potential candidate for optical applications. Huge photoluminescence emission observed in the visible region is attributed to Mn3+ ions. The temperature dependence of molar susceptibility data indicates a paramagnetic to antiferromagnetic transition around 195 K. The possible super exchange paths for antiferromagnetic interaction are Ru5+- 4d3 (t2g3eg0) − O1 − Ru5+- 4d3 (t2g3eg0) along the z axis, or Ru5+- 4d3 (t2g3eg0) − O2 − Ru5+- 4d3 (t2g3eg0) in the xy-plane, with the angles between these orbitals being nearly 180°. At low temperatures under a 10,000 Oe field, spin glass type magnetic behaviour is observed. The effective magnetic moment (6.17 μB) obtained from the Curie-Weiss fit from 260 K to 290 K nearly matched with the theoretical resultant effective moment (6.24 μB) by considering Mn3+ ions in HS state and Ru5+ ions.Specific heat measurements revealed no long-range magnetic ordering down to 2 K, further suggesting the role of cationic disorder in the magnetic behaviour of Sr2MnRuO6.

Structural, thermodynamic, and magnetic properties of SrFe12O19 hexaferrite modified by co-substitution of Cu and Gd.

A hard magnetic system of SrFe12O19 nanomaterial was modified according to the composition of Sr0.95Gd0.05Fe12-xCuxO19 with x = 0.0, 0.30, and 0.60 using the sol-gel technique. The structures of the samples were evaluated using X-ray diffraction (XRD) along with Rietveld refinement, and an M-type hexaferrite with a hexagonal structure was confirmed with a trace amount of the α-Fe2O3 phase. In addition, transmission electron microscopy (TEM) analysis revealed polycrystalline nanoplates in all samples. Furthermore, the bond structures of the octahedral and tetrahedral sites along with the thermodynamic properties of these ferrites were extracted from the FTIR spectra at room temperature. The Debye temperature (θD) decreased from 755.9 K to 749.3 K due to the co-substitution of Gd3+ at Sr2+ and Cu2+ at Fe3+. The magnetic hysteresis (M-H) measurements revealed that the coercivity decreased from 5.3 kOe to 1.5 kOe along with the highest magnetization saturation (Ms) of 65.2 emu g-1 for the composition Sr0.95Gd0.05Fe11.7Cu0.3O19, which is suitable for industrial application. The effect of local crystalline anisotropy in magnetization was explored using the law of approach to saturation (LAS). Finally, thermo-magnetization was recorded in the range from 400 K to 5 K for cooling under zero field and in the presence of a 100 Oe field, and magnetic transitions were tracked due to the introduction of the foreign atoms of Gd and Cu into SrFe12O19.

Two Pairs of Homochiral Parallelogram-like Dy4 Cluster Complexes with Strong Magneto-Optical Properties.

Two pairs of homochiral Dy(III) tetranuclear cluster complexes derived from (+)/(-)-3-trifluoroacetyl camphor (D-Htfc/L-Htfc), [Dy4(OH)2(L1)4(D-tfc)2(DMF)2]·4DMF (D-1) [H2L1 = (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol)]/[Dy4(OH)2(L1)4(L-tfc)2(DMF)2]·4DMF (L-1) and [Dy4(OH)2(L2)4(D-tfc)2(DMF)2]·2H2O·3MeCN (D-2) [H2L2 = (E)-3-(2-hydroxy-3-methoxybenzylideneamino)naphthalen-2-ol]/[Dy4(OH)2(L2)4(L-tfc)2(DMF)2]·2H2O·3MeCN (L-2), were synthesized at room temperature, which have a Dy4 parallelogram-like core. The magnetic studies revealed that D-1 exhibits single-molecule magnet (SMM) behavior under zero dc magnetic field, and its magnetic relaxation has a distinct Raman process in addition to the Orbach process, with the Ueff/k value of 57.5 K and the C value of 28.27 s-1K-2.14; while D-2 displays dual magnetic relaxation behavior at 0 Oe field, with the Ueff/k value 114.8 K for the slow relaxation process (SR) and the C value of 10.656 s-1K-5.80 for the fast relaxation process (FR), respectively. Theoretical calculations indicated that the conjugated groups (phenyl vs naphthyl) of the Schiff base bridging ligands (H2L1 and H2L2) significantly affect the intramolecular magnetic interactions between the Dy3+ ions and ultimately lead to different relaxations. Furthermore, magnetic circular dichroism (MCD) measurements showed that these two pairs of Dy4 enantiomers exhibit strong room temperature magneto-optical Faraday effects; notably, increasing the conjugated group on the Schiff base bridging ligand is beneficial to enhancing the magneto-optical Faraday effects.

Facile preparation of novel type polymethyl methacrylate/CoFe2O4/BNNS composite cements and their caloric performance in alternating magnetic fields

AbstractMagnetic hyperthermia generated by functionalized bone cement is a promising approach to treat postosteocarcinoma cancer regeneration. However, it is crucial to minimize the magnetic field intensity using localized high‐caloric‐generating nanoparticles to avoid the potential hazards of electromagnetic field exposure to living organisms. Herein, in situ hydrothermally synthesized CoFe2O4 (CoFe) nanoparticles and boron nitride nanosheet (BNNS)–supported CoFe complexes (BNCoFe) are incorporated into polymethyl methacrylate (PMMA) cement to prepare a composite implant with high‐intensity magnetic–thermal performance and safety. The results show that the CoFe nanoparticles (size = ~70 nm) anchored on BNNS surfaces exhibit a maximum magnetic–thermal ablation temperature of ~42°C within 50 s under an alternating magnetic field of 400 KHz (field frequency) and 30 Oe (field intensity) in vitro. Furthermore, the incorporation of BNNSs into the PMMA matrix notably increases the thermal conductivity of PMMA from 0.07 to 0.25 W mK−1 and improves its mechanical properties (compressive strength increases from 74.0 ± 1.6 to 81.0 ± 1.0 MPa), which is attributed to the crystalline structure of BNNSs in the PMMA matrix. Inductively coupled plasma analysis shows a considerably reduced Co2+ ion release from PMMA/BNCoFe, indicating its potential as a safe implantation material for hyperthermia treatment.

Bifunctional Lanthanide-Based Coordination Polymers: Conversion of CO2 and Highly Selective Luminescence Sensing for Acetylacetone.

A series of bifunctional Ln(III)-based coordination polymers (CPs) {Ln(L)(DMA)2(NO3)}n [Ln(III) = Eu (1), Gd (2), and Dy (3); organic ligand H2L = 2,2'-(1,3,5,7-tetrahydroxyoctahydro-4,8-ethanopyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)diacetic acid)] have been successfully synthesized. CPs 1-3 are isostructural and constructed from the dimeric Ln2 unit in which two adjacent LnIII ions are bridged by two μ3-carboxyl oxygens, and the Ln2 dimeric unit is connected by two NO3- ions, four DMA molecules, and four completely protonated L2- ligands forming a 2D layer structure. The magnetic research reveals that CP 2 shows a significant cryogenic magnetocaloric effect (-ΔSm = 22.9 J kg-1 K-1; T = 2.0 K and ΔH = 7.0 T), whereas CP 3 exhibits slow magnetic relaxation property under Hdc = 0 Oe field. Additionally, the luminescence explorations revealed that CP 1 can act as a recyclable luminescent probe for pollutant acetylacetone among various small organic solvent molecules, and the corresponding detection limit is 10-7 mol/L. More importantly, CP 1 also exhibits good catalytic performance in the cycloaddition reaction of CO2 and epoxides or cyanamides under mild conditions. As far as we know, CP 1 represents the first bifunctional lanthanide homogeneous catalyst that can efficiently catalyze the reaction of cyanamides/epoxides with CO2 simultaneously.

Superconductivity in null-scattering Ti:Zr alloy

Null-scattering Ti:Zr alloy (Ti67.6Zr32.4) is widely used in neutron scattering for sample containers, pressure cells and gaskets since it does not produce contaminant Bragg reflections from the sample environment. Here we report superconductivity in this material with critical temperature T c = 1.4 K, lower critical field Hc1≈ 100 Oe and upper critical field Hc2 ≈ 4500 Oe. These properties are largely independent of the amount of a small quantity of ferromagnetic iron found in materials of all providers. Our findings bear on the use of Ti:Zr in neutron scattering experiments at applied field and low temperatures.

A spherical capped square antiprismatic DyIII complex encapsulated three acylhydrazone Schiff base ligands behaving field-induced single-ion magnet behaviour

One mononuclear DyIII based complex, [Dy(L)3]·0·25H2O (1) (HL= N'-(2-hydroxybenzoyl)pyridine-2-carbohydrazonamide) has been successfully synthesized and systematically characterized. Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system with space group P/21. The nine-coordinated DyIII ion in 1 adopts distorted spherical capped square antiprism configuration (C4v-CSAPR) with three tridentate coordination pockets. In addition, the alternating-current (ac) magnetic susceptibility investigations show that 1 exhibits slow magnetic relaxation behavior under an applied 1000 Oe field with effective energy barrier (Ueff) of 83.10 K. To understand the magnetic behaviour in depth, the magnetic axes and magneto-structural correlations are analyzed to reveal that the coordination of three ligands effectively enhances the axiality of the nine-coordinated mononuclear DyIII complexes, thereby exhibiting the slow magnetic relaxation behaviour. This work provides a strategy to effectively improve the performance of single-ion magnets (SIMs) by introducing more ligands around the DyIII ion, and regularizing the coordination configuration of the DyIII ion towards an axial-type structure.

Плёнки FeZrN: статические и СВЧ магнитные свойства

The phase-structural state, magnetic structure parameters, static and microwave magnetic properties of Fe81 – 74Zr2 – 5N17 – 21 films prepared by reactive magnetron deposition were studied. As the Zr and N contents increase, the film structure changes from, so-called, mixed structure (grain size 3 – 6 nm of nanocrystalline α-Fe(Zr,N) + fcc nitride) to amorphous one. The film magnetic structure parameters (effective anisotropy field of stochastic domains D1/2〈Ha〉 = 11.8 ± 8 Oe and effective local anisotropy field D1/2Ha = 880 ± 700 Oe), saturation magnetization Ms (1.8 ± 0.3 T), coercive field Hc (11 ± 2 Oe), and the real permeability µ′ (80 ± 30), retaining its value at frequencies up to 3 GHz, were determined. The values of the initial permeability µ0 (70 ± 21) obtained from the hysteresis and the real permeability µ′ (80 ± 30) obtained from microwave measurements are in good agreement. The correlation between the static magnetic properties, the stochastic magnetic structure parameters and the real permeability µ′ was considered. There is no any sign on ferromagnetic resonance in the studied frequency range. However the Acher’s coefficient value (less than 0.38) for this frequency range indicates the possibility of ferromagnetic resonance at higher frequencies.

Enhanced magnetic properties in Sm3+ substituted SrFe12O19

M- Type hexaferrite captivates researchers and industrialists for its diverse usage and applications in different fields such as permanent magnets, storage devices, recording media, radar absorbing materials and many more. In this work, Sm3+ substituted Strontium hexaferrite, Sr1-xSmxFe12O19 (x = 0, 0.05) is synthesized by using ethylene glycol aided sol–gel auto combustion technique. X-Ray Diffraction Technique is employed for the understanding of various structural features. Phase purity of the prepared samples is authenticated by performing Rietveld refinement method. All the studied samples crystallizes in hexagonal magneto-plumbite phase with P63/mmc space group. Crystallite sizes are determined using Scherer equation. Field Emission Scanning Electron Microscopy is used for morphological analysis. Average particle size decreases with Sm3+ substitution in comparison with parent one. Both field and temperature dependent magnetization measurements are accomplished for magnetic properties analysis. Hysteresis curves show Coercivity (Hc) value increases more than two times and saturation magnetization (MS) decreases slightly as compared to parent sample which clearly indicates that the sample can be used as hard ferrites. M−T measurements are carried out with the application of 500 Oe field. Both the sample show transition around 500 °C temperature. Substituted sample also shows a prominent Hopkinson peak in comparison with parent sample.

Sign reversal of both spontaneous and conventional exchange bias in nanoparticles of Y2FeCrO6 double perovskite

Single-phase nanoparticles sample of Y2FeCrO6 double perovskite with an average particle size of 67 nm was prepared and its structural and magnetic behavior is reported. Magnetization vs temperature (M–T) study revealed that the Neel temperature, TN is 327 K, which is greater than the previous finding [Maiti et al., J. Phys. D: Appl. Phys. 46, 415303 (2013)]. Super-exchange interactions in Cr3+–O–Cr3+ and Fe3+–O–Fe3+ networks are responsible for AFM transition. Magnetization reversal (MR) with a high compensation temperature Tcomp = 192 K and sign reversal in both spontaneous and conventional exchange bias fields are observed. In addition, a spin reorientation is observed at TSR ∼ 30 K. At 5 K, a zero-field cooled spontaneous exchange bias (SEB) field of 265 Oe is observed. At the same temperature, after field cooling the sample at 0.5 T, the maximum value of the exchange bias field (CEB) is found to be 2.1 kOe. The SEB shows a sign reversal across TSR, and the CEB reverses its sign across Tcomp. The observed thermal hysteresis of magnetization indicates a first-order phase transition. The loop width of magnetic hysteresis as a function of magnetization exhibits a double peak confirming the multiple magnetic phase behavior. Bipolar switching of magnetization has been demonstrated at 50 K. The competition between single-ion anisotropy and Dzyaloshinsky–Moriya interaction is responsible for the above behaviors.

In a search for effective giant magnetoelectric coupling: Magnetically induced elastic resonance in Ni-Mn-Ga/P(VDF-TrFE) composites

Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) is a piezoelectric polymer suitable for applications in electromechanical and magnetoelectric (ME) systems. Ni-Mn-Ga alloys exhibit a giant magnetoelastic response related to their structural transformations of martensitic type, accompanied by noticeable volume changes. Together, in a thin film composite containing an ensemble of Ni-Mn-Ga particles (10 wt.%) distributed in the P(VDF-TrFE) piezopolymer, they ensure an unprecedented resonance amplification of the ME effect. Thus, a giant value of ME coefficient of 6.05 V·cm−1· Oe−1 under AC magnetic drive field of 0.2 Oe and DC bias field of 1300 Oe is experimentally observed and discussed. The physical mechanism of the proposed ME response amplification has been explained theoretically through the volume magnetostriction of the magnetostrictive particles and resonant elastic oscillation of the piezoelectric polymer matrix.

Enhancing the spin–orbit torque efficiency in Pt/CoFeB/Pt based perpendicularly magnetized system

In the recent past, current-induced magnetization reversal (CIMR) has been extensively studied on the heterostructures prepared with heavy metal (HM) and ferromagnet (FM) having spin–orbit torque (SOT). The critical current density (Jc) for magnetization switching depends on the SOT efficiency. In this study, we have chosen Ta/Pt/CoFeB/Pt/Ta/CoFeB/Pt heterostructure having perpendicular magnetic anisotropy (PMA) with broken lateral symmetry and an in-plane magnetized (IMA) ferromagnetic layer on top of the Ta layer. In this heterostructure, we have utilized the SOT originated by the spin-Hall effect that arises from two materials having opposite spin Hall angles i.e. the bottom Pt and the top Ta layer. We have also introduced lateral space inversion asymmetry (SIA) that combines both damping-like and field-like field. The enhanced spin Hall angle, the stray field by IMA ferromagnetic layer, and the lateral SIA effect jointly enhances the SOT efficiency of the system to reduce the Jc for CIMR. We have found that the SOT efficiency and the effective spin Hall angle of our newly designed heterostructure to be 106 Oe/1011A/m2 and 0.23, respectively. Thus we have achieved CIMR with a lower critical current density of 8.65×1010 A/m2 and 3.35×1010 A/m2 at 0 Oe and 600 Oe field applied in-plane (IP), respectively. Due to the lower Jc for CIMR our newly designed heterostructure has potential in low-power magnetic data storage applications.

Air-Stable Dy(III)-Macrocycle Enantiomers: From Chiral to Polar Space Group

Air-Stable Dy(III)-Macrocycle Enantiomers: From Chiral to Polar Space Group

Heating loss mechanism in β-NaFeO2 nanoparticles for cancer treatment under alternating field

The induction heating loss mechanism in nanofluids prepared using synthesized β-NaFeO2 nanoparticles has been discussed concerning optimization of magnetic relaxation (Neel and Brownian) losses, specific absorption rate (SAR), intrinsic loss power (ILP)as well as the concentration of nanoparticles. The highest value of SAR for β-NaFeO2 nanoparticles is 705.86 W/g at 335.2 Oe field and 267 kHz frequency. The value of Brownian and total relaxation time has been calculated theoretically and found to be τB= 6.126 × 10−4 sand τ = 2.668 × 10−7 s, respectively. For Hyperthermia treatment, 2 to 5 mg/mL is the best suitable lowest concentration to achieve high SAR and ILP under applied field. The maximum value of ILP observed is 1.49 nHm2/kg. The calculated theoretical and experimental parameters of induction heating make synthesized β-NaFeO2 nanoparticles suitable for the treatment of cancer via Hyperthermia.

Anomalous anisotropy of the lower critical field and Meissner effect in UTe2

We report on low temperature susceptibility and magnetization measurements made on single crystals of the recently discovered heavy-fermion superconductor UTe$_2$ and compare the results with the two ambient pressure ferromagnetic superconductors URhGe and UCoGe. Hysteresis curves in the superconducting phase show a familiar diamond shape superimposed on a large paramagnetic background. The Meissner state was measured by zero field cooling in small fields of a few Oe as well as ac susceptibility measurements in small fields and resulted in 100\% shielding, with a sharp transition. However the field cooling Meissner-Ochsenfeld effect (expulsion of flux) was negligible in fields greater than just a few Oe, but becomes nearly 30\% of the perfect diamagnetic signal when the field was reduced to 0.01~Oe. The critical current due to flux pinning was studied by ac susceptibility techniques. Over the range in fields and temperature of this study, no signature of a ferromagnetic transition could be discerned. The lower critical field $H_{\rm c1}$ has been measured along the three crystalographic axes, and surprisingly, the anisotropy of $H_{\rm c1}$ contradicts that of the upper critical field. We discuss this discrepancy and show that it may provide additional support for a magnetic field-dependent pairing mediated by ferromagnetic fluctuations in UTe$_2$.

A novel Dy4 cluster constructed by an 8‑hydroxyquinoline Schiff base showing remarkable single molecule magnet behavior

The construction of polynuclear Ln(III)-based clusters toward interesting topological structures and outstanding magnetic properties is a critical challenge for chemists. Herein, by using a flexible Schiff base ligand H2L, a novel Dy4 cluster with the formula {Dy4(acac)4L4}·solvent (1) (Hacac = acetylacetone, and H2L = pyridine-2-carboxylic acid (8-hydroxy-quinolin-2-ylmethylene)-hydrazide), has been synthesized, structurally and magnetically studied. The X-ray structural analysis suggests cluster 1 is a tetranuclear dysprosium compound, and the four central Dy(III) ions are connected by eight bridging N atoms of four H2L forming a quadrilateral Dy4 core. It is interesting that more than one magnetic relaxation processes were clearly observed in the 1-Dy4 cluster under Hdc = 0 Oe field.

Heating Loss Mechanism in β-NaFeO <sub>2</sub> Nanoparticles for Cancer Treatment Under Alternating Field

The induction heating loss mechanism in nanofluids prepared using synthesized β-NaFeO2 nanoparticles have been discussed with respect to optimization of magnetic relaxation (Neel and Brownian) losses, specific absorption rate (SAR), intrinsic loss power (ILP)as well as concentration of nanoparticles. The highest value of SAR for β-NaFeO2 nanoparticles has been found to be 282.3 W/g at 335.2 Oe field and 267 kHz frequency.The value of Brownian and total relaxation time has been calculated theoretically and found to be τΒ= 6.126x10-4 sand τ= 2.668x10

Magnetoelectric response in lead-free Na0.4K0.1Bi0.5TiO3/NiFe2O4 laminated composites

Lead-free Na0.4K0.1Bi0.5TiO3 (NKBT) and NiFe2O4 (NFO) ceramics are synthesized by solid-state reaction, and the laminated NKBT/NFO composites have been prepared by gluing the sintered discs with silver-epoxy. The measured parameters, dielectric constant (ε′) ∼1450 at 1 kHz, remanent polarization (Pr)∼39 μC/cm2, coercive electric field (Ec)∼27 kV/cm and maximum strain (Smax)∼0.3 % of NKBT along with saturation magnetization (Ms)∼49 emu/g, coercive magnetic field (Hc)∼27 Oe and magnetostriction (λ)∼-30 ppm of NFO, makes them suitable materials to evaluate as laminated magnetoelectric (ME) composites. A maximum ME response of 37, 67 and 86 mV/cm Oe at Hdc∼350−400 Oe field and 1 kHz frequency is observed for NKBT/NFO, NKBT/NFO/NKBT and NFO/NKBT/NFO layered composites, respectively. The high ME response at reasonable fields implies that NKBT/NFO laminated composite is a worthy lead-free candidate for ME sensor and energy harvesting applications.

Exchange bias and spin-reorientation transition in α-Fe/PrDyCoFeB core/shell microwires

Magnetic anisotropy and interface exchange interaction were analyzed in α-Fe core microwire covered with PrDyCoFeB amorphous shell. The α-Fe/PrDyCoFeB core/shell microwires were grown by pendant drop melt extraction technique providing separation of the α-Fe and PrDyCoFeB phases during the ultrafast cooling. Low saturation field of the core ~100 Oe and high saturation field of amorphous shell ~10 kOe with zero coercivity were distinguished from angular dependences of the magnetic moment, recorded in low and high magnetic fields. Sharp decrease of the longitudinal magnetization, effective anisotropy field and magnetic susceptibility have been observed below the critical temperature, Tcrit = 240 K, in zero field. The Almeida-Thouless transition from ferrimagnetic state to Ising spin glass state has been revealed in PrDyCoFeB amorphous shell. Such spin reorientation transition is very attractive for magnetocaloric applications. We found exchange bias effect controlled by exchange coupling between ferromagnetic core and ferrimagnetic shell. The significance of the obtained data lies in possible applications of the core/shell microwires for tweezers with magnetic moment, stepwise changing in external field. Exchange bias in core-shell interface provides determined initial state of the microwire used as working media of field sensor. The sharp decrease of the magnetization associating with spin-reorientation transition looks very promising for magnetocaloric applications close to room temperature.