Magnetic Glass Research Articles

Preparation and characterization of quaternary magnetic Fe80-xCoxP14B6 bulk metallic glasses

A new series of quaternary magnetic Fe80-xCoxP14B6 (x = 20, 30, 40, 50, 60 at. %) bulk metallic glasses (BMGs) has been prepared by combining fluxing treatment and J-quenching technique, and the maximum critical diameter for fully glass formation reaches up to 2.0 mm for x = 40 among this series of FeCo-based BMGs. The effects of Co content on glass-forming ability, thermal stability, mechanical and magnetic properties of the present FeCo-based BMGs have been systematically investigated. It is found that the highest thermal stability, namely the highest glass transition temperature (Tg) and the onset crystallization temperature (Tx), is achieved when the ratio of Fe and Co contents is 1:1 in the present FeCo-based BMGs. It should be noted that the maximum Curie temperature reaches 791 K when x = 40, which is the highest Curie temperature for (Fe, Co, Ni)-based BMGs so far as is known. Moreover, the present FeCo-based BMGs exhibit very good soft magnetic properties and large room plasticity, which are promising for potential industrial application as high performance functional and structural materials.

Drug delivery property, bactericidal property and cytocompatibility of magnetic mesoporous bioactive glass

A multifunctional magnetic mesoporous bioactive glass (MMBG) has been widely used for a drug delivery system, but its biological properties have been rarely reported. Herein, the effects of mesopores and Fe3O4 nanoparticles on drug loading–release property, bactericidal property and biocompatibility have been investigated by using mesoporous bioactive glass (MBG) and non-mesoporous bioactive glass (NBG) as control samples. Both MMBG and MBG have better drug loading efficiency than NBG because they possess ordered mesoporous channels, big specific surface areas and high pore volumes. As compared with MBG, the Fe3O4 nanoparticles in MMBG not only provide magnetic property, but also improve sustained drug release property. For gentamicin-loaded MMBG (Gent-MMBG), the sustained release of gentamicin and the Fe3O4 nanoparticles minimize bacterial adhesion significantly and prevent biofilm formation against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Moreover, the magnetic Fe3O4 nanoparticles in MMBG can promote crucial cell functions such as cell adhesion, spreading and proliferation. The excellent biocompatibility and drug delivery property of MMBG suggest that Gent-MMBG has great potentials for treatment of implant-associated infections.

Structural, dielectric, thermal and electron magnetic resonance studies of magnetic porous glasses filled with ferroelectrics

Magnetic, dielectric and thermal properties of multiferroic nanoparticles were synthesized with a novel magnetic porous glass-based method. We report the properties of empty magnetic porous glasses and ones filled with NaNO2 or KNO3 ferroelectrics. It was shown that the ferroelectric nanocomposites obtained on the basis of porous glasses exhibit both ferroelectric and ferromagnetic properties. The dielectric permittivity and the ac conductivity were discussed as a function of frequency and temperature. For all obtained multiferroic nanocomposites the dielectric results show a ferroelectric-like behavior. The specific heat was measured using the DSC method and the anomaly of the ferroelectric phase transitions was indicated. We report on the magnetic properties of multiferroic nanocomposites investigated by EMR at two frequencies (X, S band). Both the temperature and the frequency dependencies of the narrow and broad resonance lines fulfilled a condition for the superparamagnetic behavior of porous glasses with ferroelectric particles inside. Finally, we were able to measure the ferroelectric polarization for magnetic porous glasses filled with NaNO2 ferroelectrics. The particle-size dependent magnetic, dielectric and thermal properties of the obtained multiferroics nanocomposites were studied.

Understanding the magnetic behavior of heat treated CaO–P2O5–Na2O–Fe2O3–SiO2 bioactive glass using electron paramagnetic resonance studies

Bioactive glass of composition 41CaO–44SiO2–4P2O5–8Fe2O3–3Na2O has been heat treated in the temperature (TA) range of 750–1150°C for time periods (tA) ranging from 1h to 3h to yield magnetic bioactive glass ceramics (MBCs). X-ray diffraction studies indicate the presence of bone mineral (hydroxyapatite and wollastonite) and magnetic (magnetite and α-hematite) phases in nanocrystalline form in the MBCs. Electron paramagnetic resonance (EPR) study was carried out to understand the variation in saturation magnetization and coercivity of the MBCs with TA and tA. These studies reveal the nature and amount of iron ions present in the MBCs and their interaction in the glassy oxide matrix as a function of annealing parameters. The deterioration in the magnetic properties of the glass heat treated above 1050°C is attributed to the crystallization of the non-magnetic α-hematite phase. These results are expected to be useful in the application of these MBCs as thermoseeds in hyperthermia treatment of cancer.

Potential of Metallic Glass Thin Films as a Soft Magnetic Underlayer for <inline-formula> <tex-math notation="TeX">${\rm L}1_{0}$ </tex-math></inline-formula> FePt-Based Recording Media

We report on the use of metallic glass (FeHfNbYB) thin film as a soft magnetic underlayer for the fabrication of L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> FePt-based bit patterned recording media (BPM). Preferred oriented phase of L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (111) FePt is obtained either by depositing it in situ on a heated soft magnetic metallic glass/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si or at room temperature (FePt/metallic glass/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si) followed by annealing at 400 °C-450 °C for 20 min. Fabrication of recoding bits of size ~2 μm to 20 nm is demonstrated using electron beam lithography. Magnetic measurements on ~500 nm bit patterns show a narrow switching field (SF) distribution with SF of ~3 kOe. The ability to read/write this BPM is demonstrated with a commercial head in perpendicular geometry in a static tester. Results strongly suggest that the soft magnetic metallic glass thin films can solve the problem of writability in high anisotropy L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> FePt-based recording media.

Modelling magnetostructural textures in magnetic shape‐memory alloys: Strain and magnetic glass behaviour

In this paper, we propose a model that combines a Landau free energy part and a micromagnetic free energy part aimed at describing a magnetostructural multiferroic. We show that in the limit of high‐elastic anisotropy and strong magnetostructural interplay, the model is able to reproduce characteristic strain and magnetization configurations typical of magnetic shape‐memory materials. For low‐elastic anisotropy, in the presence of disorder arising from compositional fluctuations giving rise to a distribution of local transition temperatures, the model is able to reproduce strain glass behaviour. In this case, the temperature dependence of the magnetization measured after zero magnetic field cooling deviates from the magnetization measured after magnetic field cooling protocol, which proves that the strain glass behaviour induces non‐ergodicity in the magnetic degrees of freedom as well.

Novel Phenolic Biosensor Based on a Magnetic Polydopamine-Laccase-Nickel Nanoparticle Loaded Carbon Nanofiber Composite

A novel phenolic biosensor was prepared on the basis of a composite of polydopamine (PDA)-laccase (Lac)-nickel nanoparticle loaded carbon nanofibers (NiCNFs). First, NiCNFs were fabricated by a combination of electrospinning and a high temperature carbonization technique. Subsequently, the magnetic composite was obtained through one-pot Lac-catalyzed oxidation of dopamine (DA) in an aqueous suspension containing Lac, NiCNFs, and DA. Finally, a magnetic glass carbon electrode (MGCE) was employed to separate and immobilize the composite; the modified electrode was then denoted as PDA-Lac-NiCNFs/MGCE. Fourier transform infrared (FT-IR) spectra and cyclic voltammetry (CV) analyses revealed the NiCNFs had good biocompatibility for Lac immobilization and greatly facilitated the direct electron transfer between Lac and electrode surface. The immobilized Lac showed a pair of stable and well-defined redox peaks, and the electrochemical behavior of Lac was a surface-controlled process in pH 5.5 acetate buffer solution. The PDA-Lac-NiCNFs/MGCE for biosensing of catechol exhibited a sensitivity of 25 μA mM(-1) cm(-2), a detection limit of 0.69 μM (S/N = 3), and a linear range from 1 μM to 9.1 mM, as well as good selectivity and stability. Meanwhile, this novel biosensor demonstrated its promising application in detecting catechol in real water samples.

A spin glass perspective on ferroic glasses

A range of ferroic glasses, magnetic, polar, relaxor and strain glasses, are considered together from the perspective of spin glasses. Simple mathematical modelling is shown to provide a possible conceptual unification to back similarities of experimental observations, without considering all possible complexities and alternatives.

Sputtering perpendicular magnetic anisotropy CoPt thin film on glass substrate at room temperature

[Co1.0/Pt0.75]n multilayers consisting of 1.0-nm-thick Co and 0.75-nm-thick Pt layers with n = 2–6 were grown on glass substrates with and without a Pt underlayer at room temperature (RT). In this study, the effects of total thickness and Pt underlayer on magnetic properties and microstructures are investigated. Without a Pt underlayer, the [Co1.0/Pt0.75]n film exhibits soft magnetic behaviors due to poor crystallization. After the inclusion of a Pt underlayer between magnetic layer and glass substrate, the [Co1.0/Pt0.75]n films show significant perpendicular magnetic anisotropy (PMA), out-of-plane coercivity, and squareness as the total thickness of [Co1.0/Pt0.75]n is in the range of 5.25–10.5 nm. The induced PMA is attributed to the epitaxial growth of CoPt grains along Pt(111) underlayer. The RT-prepared CoPt film with PMA shows high potential in future applications of spintronics.

Antiferromagnetic cluster spin-glass behavior in Pr117Co54.5Sn115.2 – A compound with a giant unit cell

The magnetic properties of Pr117Co54.5Sn115.2 – a member of a family of materials with a giant unit cell – have been investigated by dc magnetization, ac magnetic susceptibility, specific heat, and electrical resistivity measurements. A magnetic glassy state at freezing temperature of ∼11K was determined from the magnetic susceptibility and specific heat data. The glassy state in Pr117Co54.5Sn115.2 is not the conventional spin glass with randomly oriented magnetic moments, but it is related to clusters of atoms that exist in the complex crystal lattice of the material. Furthermore, the glassy state coexists with short range antiferromagnetic order, leading to the development of antiferromagnetic clusters. A weak anomaly in the specific heat data centered around 11K supports the formation of magnetic cluster glass state in Pr117Co54.5Sn115.2. Semiconductor-like resistivity with a negative temperature coefficient from 2 to 300K is also observed in Pr117Co54.5Sn115.2.

Study of mechanical and dielectric spectrum in YFe1-xMnxO3 ceramics

The mechanical spectra of Mn-substituted yttrium orthoferrite YFe1-xMnxO3 (x = 0, 0.2, 0.3, 0.4) ceramics were performed at kilohertz from 100 to 360 K. Two internal friction (IF) peaks are observed around 150 K and 230 K, respectively, and both the IF peaks exhibit frequency dispersion behavior. The IF peak around 150 K is associated with a step increase in the modulus and its mechanical relaxation rate follows the Vogel-Fulcher relation with τ0 = 4.45 × 10−11s, Eα = 0.03 eV, and TVF = 155 K. This IF peak can be explained in terms of a freezing of oxygen vacancies after excluding the possible magnetic spin glass transition. Another IF peak around 230 K presents a relaxation behavior and it follows Arrhenius law. Furthermore, the relaxation behavior was verified by the dielectric spectrum and it can be ascribed to the charge carrier hopping between Fe2+ and Fe3+.

Magnetic Biofilm Carriers: The Use of Novel Magnetic Foam Glass Particles in Anaerobic Digestion of Sugar Beet Silage

The use of recently developed magnetic foam glass particles for immobilization of microbial biomass was tested. The effect of the particles was illustrated at the production of biogas from sugar beet silage as the sole substrate. Lab-scale fermentation experiments were conducted using a mesophilic completely stirred tank reactor and a magnetic separator. Microscopic analysis revealed biofilm coverage of 50–60% on the surface of the particles within 110 days. It was possible to recover 76.3% of the particles from fermentation effluent by means of a separation procedure based on magnetic forces. Comparing a particle charged reactor with a control reactor showed a small performance gain. The methane rate was increased from1.18±0.09to1.25±0.06 L L−1 d−1and the methane yield was increased from0.302±0.029to0.318±0.022 L g−1(volatile solids) at an organic loading rate of3.93±0.22 g L−1 d−1(volatile solids). Maximum methane rates of 1.42 L L−1d−1at an organic loading rate of 4.60 g (volatile solids) L−1 d−1(reactor including magnetic particles) and 1.34 L L−1 d−1at 3.73 g L−1 d−1(control reactor) were achieved. Based on the results, it can be concluded that the use of magnetic particles could be an attractive option for the optimization of biogas production.

Order–Disorder Transition Involving the A-Site Cations in Ln3+Mn3V4O12 Perovskites

A crossover from the A-site-ordered double-perovskite structure with Im3̅ cubic symmetry to the simple-perovskite structure with Pnma orthorhombic symmetry is found in LnMn3V4O12 (Ln = La, Nd, Gd, Y, Lu) synthesized under high-pressure conditions. Relatively large Ln(3+) ions (La(3+), Nd(3+), and Gd(3+)) induce the a(+)a(+)a(+) in-phase cooperative tilting of the VO6 octahedra, resulting in the A-site-ordered double-perovskite structure with chemical composition Ln(3+)Mn(2+)3V(3.75+)4O12. Compounds with small Ln(3+) ions like Y(3+) and Lu(3+), on the other hand, crystallize with the Pnma simple-perovskite structure with chemical composition (Ln(3+)1/4Mn(2+)3/4)V(3.75+)O3, where the Ln(3+) and Mn(2+) ions are disordered at the A site. The random distribution of the small A-site cation induces the a(-)b(+)a(-) tilting distortion of the VO6 octahedra. The observed phase crossover is well explained by the structural stability calculation based on the bond-valence-sum model, and the most stable crystal structure gives the smallest unit-cell volume. This A-site-cation size-dependent phase transition between the A-site-ordered double-perovskite and A-site-disordered simple-perovskite structures in LnMn3V4O12 is thus a result of the structural stability due to the cooperative tilting of the VO6 octahedra. The Mn(2+) ions at the A'(A) site contribute local magnetic moments, whereas the V(3.75+) ions at the B site play a role in metallic conduction. The observed magnetic behaviors are consistent with the order-disorder distribution of the Mn(2+) ions at the A site, antiferromagnetism in the A-site-ordered double perovskites, and magnetic spin glass in the A-site-disordered simple perovskites.

Effects of Alloying Elements on the Thermal Stability and Corrosion Resistance of an Fe-based Metallic Glass with Low Glass Transition Temperature

The effects of alloying elements on the thermal stability, glass-forming ability (GFA), corrosion resistance, and magnetic and mechanical properties of a soft magnetic Fe75P10C10B5 metallic glass with a low glass transition temperature (Tg) of 723 K (450°C) were investigated. The addition of Mo, Ni, and Co significantly increased the stabilization of supercooled liquid, GFA, and corrosion resistance in the H2SO4 solution. The maximum critical diameter (dc) of 4 mm for glass formation was obtained for the Fe55Co10Ni5Mo5P10C10B5 alloy, which shows the largest supercooled liquid region (ΔTx) of 89 K (89 °C). The substitution of Cr for Mo further enhanced the corrosion resistance of the Fe55Co10Ni5Mo5P10C10B5, while the ΔTx and dc decreased. The (Fe, Ni, Co)70(Mo, Cr)5P10C10B5 bulk metallic glasses showed low Tg of 711 K to 735 K (438 °C to 462 °C), wide ΔTx of 67 K to 89 K, high saturation magnetization of 0.79 to 0.93 T, low coercive force of 2.36 to 6.61 A m−1, high compressive yield strength of 3271 to 3370 MPa, and plastic strain of 0.8 to 2.3 pct. In addition, the mechanism for enhancing stability of supercooled liquid was discussed in terms of the precipitated phases during crystallization.

Atomic-level structures and physical properties of magnetic CoSiB metallic glasses

Two CoSiB metallic glasses of low Co contents, which consist of different clusters, have recently been developed by addition of solute atoms. In this work, the atomic structure and the magnetic properties of the two CoBSi metallic glasses were elucidated by state-of-the-art extended X-ray absorption fine structure spectroscopy (EXAFS) combining with ab initio molecular-dynamics (AIMD) computational techniques. Besides, the origin of these magnetic behaviors was discussed in view of the EXAFS results and atomic structures of the metallic glasses.

Tunable resistivity in magnetic glass phase of Gd1−xCaxBaCo2O5.5

We present magnetization and resistance measurements carried out on pristine and Ca-doped Gd1−xCaxBaCo2O5.5 (x = 0.02) samples using the cooling and heating in unequal field (CHUF) protocol. The measurements reveal that the high temperature ferromagnetic phase is kinetically arrested at low temperature when the sample is cooled in a magnetic field. The volume fraction of this arrested phase increases upon Ca substitution and also by increasing the field in which the sample is cooled. Since the ferromagnetic phase is less resistive when compared to the low temperature antiferromagnetic phase, a tunable resistance is achieved in the sample by cooling in different magnetic fields. By cooling in magnetic fields of 9 T a reduction in resistivity by an order of magnitude is achieved. These results are consistent with the coexistence of the low temperature equilibrium antiferromagnetic phase with kinetically arrested high temperature ferromagnetic phase in the system.

Improved perpendicular magnetic anisotropy of Pr–Fe–B films with Ta underlayer

Abstract Perpendicular magnetic anisotropy (PMA) of sputter-prepared Pr–Fe–B films on the glass substrates were improved by inserting a Ta underlayer. Pr–Fe–B directly sputtered on glass substrate exhibits soft in-plane magnetic property due to the amorphous phase or poor crystallization. When Ta layer is introduced as an underlayer, strong PMA with attractive hard magnetic properties are obtained. Their magnetic properties highly depend on the thickness of Ta underlayer ( t ). Large out-of-plane coercivity ( H c⊥ > 800 kA/m) is attained for t in the range of 10–75 nm, where the Pr–Fe–B film sputtered on 50-nm-thick Ta underlayer shows stronger PMA due to promotion of the formation for the Pr 2 Fe 14 B phase with Ta underlayer. Therefore, it was demonstrated that inserting a Ta underlayer with suitable t (∼50 nm) between magnetic layer and glass substrate promotes to obtain Pr–Fe–B film with excellent PMA.

Conductive and magnetic glass microsphere/cobalt composites prepared via an electroless plating route

Glass microsphere/cobalt composites were successfully prepared by an electroless plating method in alkaline solution. The as-obtained samples were characterized by XRD, SEM, and VSM techniques. It was found that the concentrations of cobalt salt and aqueous ammonia greatly influenced the microstructure of cobalt coatings. A compact, uniform and continuous cobalt coating could be deposited on the surface of the glass microspheres by adjusting the synthetic parameters. The cobalt layer possessed hexagonal-close-packed phase structure. The magnetic measurement demonstrated that the glass microsphere/cobalt composites exhibited ferromagnetic nature with saturation magnetization of 21.1emu/g and coercivity of 382.9Oe, respectively. Compared to the cobalt bulk, the composites showed a decreased saturation magnetization value but an enhanced coercivity.

Observation of bi-relaxor characteristic in multiferroic 0.70Bi0.90Ca0.10FeO3–0.30PbTiO3 ceramics

The coexistence of bi-relaxor property, i.e. ferroelectric relaxor as well as spin glass type behaviour, is observed in disordered multiferroic ceramic 0.70Bi0.90Ca0.10FeO3–0.30PbTiO3. The real parts of dielectric permittivity and magnetic susceptibility show pronounced frequency dispersion near the corresponding phase transition temperatures, namely, Tc ≈ 550 K and TN ≈ 110 K, respectively. The relaxor behaviour observed in temperature-dependent dielectric constant measurement is confirmed by fitting of the Vogel–Fulcher equation. Similarly, magnetic spin glass behaviour is proven by power law fitting. The origin of such bi-relaxor in the present system can be attributed to the disorder and frustration among the uncompensated spins of the Fe-ion. This has been confirmed by analysing the x-ray photoelectron (XPS) spectrum of the sample under investigation. Using FESEM micrographs, the coexistence of nano-sized and bulk grains is shown. The importance of such coexistence is discussed and also presented in the paper.

Effect of P2O5 and MnO2 on crystallization of magnetic glass ceramics

This work pointed out the effect of adding P2O5 and/or MnO2 on the crystallization behavior of magnetic glass ceramic in the system Fe2O3·ZnO·CaO·SiO2·B2O3. The differential thermal analysis of the quenched samples revealed decrease in the thermal effects by adding P2O5 and/or MnO2 to the base sample. The X-ray diffraction patterns show the development of nanometric magnetite crystals in a glassy matrix. Heat treatment at 800°C for 2h, under reducing atmosphere, caused an increase in the amount of the crystallized magnetite with the appearance of minor hematite and Ca2SiO4. The transmission electron microscope revealed a crystallite size in the range 10–30nm. Magnetic hysteresis cycles were analyzed with a maximum applied field of 25kOe at room temperature. The prepared magnetic glass ceramics are expected to be useful for localized treatment of cancer.