Search results for "Coercivity"
showing 10 items of 74 documents
Magnetic Langmuir–Blodgett films of ferritin with different iron loadings
2005
Abstract Magnetic Langmuir–Blodgett multilayers of two ferritin molecules 1 and 2 , containing, respectively, 4220 and 3062 Fe atoms have been prepared by using the adsorption properties of a 6/1 mixed monolayer of dioctadecyldimethylammonium bromide (DODABr) and methyl stearate (SME). Transfer ratios close to unity were reached giving rise to LB films with a strong red colour. Infrared and UV–vis spectroscopy indicates that ferritin molecules are incorporated within the LB films. Magnetic measurements show that the superparamagnetic properties of these molecules are preserved. Thus, a marked hysteresis loop of magnetisation is obtained for LB films of 1 and 2 with a coercive field of 3400 …
Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO 3
2019
We report a combined study of imaging the antiferromagnetic (AFM) spin structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO3(1 1 0) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO3/Ta bilayers exhibit a positive SMR, in contrast to the negative SMR expected in previously studied collinear AFMs. The SMR amplitude increases linearly with increasing external magnetic field at higher magnetic fields, suggesting that field-induced canting of …
Emergence of the stripe-domain phase in patterned permalloy films
2016
The occurrence of stripe domains in ferromagnetic Permalloy (Py=Fe$_{20}$Ni$_{80}$) is a well known phenomenon which has been extensively observed and characterized. This peculiar magnetic configuration appears only in films with a thickness above a critical value ($d_{cr}$), which is strongly determined by the sputtering conditions (i.e. deposition rate, temperature, magnetic field). So far, $d_{cr}$ has usually been presented as the boundary between the homogeneous (H) and stripe-domains (SD) regime, respectively below and above $d_{cr}$. In this work we study the transition from the H to the SD regime in thin films and microstructured bridges of Py with different thicknesses. We find the…
Some New Ceramics and Thin Films of Pb(B 3+ ,Nb)TiO 3 -PbTiO 3 System
2002
The structure, dielectric, and electromechanical properties of (1-x)Pb(B 3+ ,Nb)TiO 3 -xPbTiO 3 binary systems (B=Lu,Er,To,Ho) are reported. High values of the electromechanical coupling coefficien...
SrTiO3and Pr Effects on Structural, Dielectric and Ferroelectric Properties of Na0.5Bi0.5TiO3Ceramic
2015
[(Na0.5Bi0.5TiO3)0.7Sr0.3]1-xPrxTiO3(NBTS30P) (0 ≤ x ≤ 0.025) ceramics were prepared by solid-state synthesis process. Their crystal structure, microstructure dielectric and ferroelectric properties were studied. XRD data show that all of the ceramics possess a single perovskite phase. SEM results confirm that the ceramics are well sintered and exhibit relative densities higher than 97%. The results also reveal that the microstructure of the different compositions do not show a significant variation. The praseodymium (Pr) substitution to NBTS30 results in a change of crystal structure from cubic to tetragonal at x = 0.025. At the same time, electric permittivity decreases, the maximum is br…
Formation of Layers of Diverse Stoichiometric and Phase Composition in Lithium Tantalate Crystals at Treatment by Vapour Transport Equilibration
2012
Layers from tens to hundreds of microns thick of a different phase composition and stoichiometry are shown to form in lithium tantalate crystals subjected to treatment by vapor transport equilibration in lithium vapour. The 500 microns thick stoichiometric (Li/Ta ≈ 1) layers have ten times lower values of the coercive field compared with congruent lithium tantalate. As electrical measurements suggest, a new polar structure of phase transition at ∼120°C is possibly formed within a thin (30 μm) surface layer of the lithium tantalate sample after vapour transport equilibration treatment.
Physical properties of ferroelectric film with continuous space charge distribution
2014
We present a theory of ferroelectric phase transitions in a film with a homogeneously distributed space charge leading to the so-called built-in polarization. On the base of our complete solution of the problem of continuous space charge distribution in a ferroelectric film, we calculate the ferroelectric phase transition temperature , spatial polarization distribution in paraelectric and ferroelectric phases as well as hysteresis loop in the ferroelectric phase. We have shown that the presence of continuous space charge in a film inhibits the ferroelectricity in it: it lowers the ferroelectric phase transition temperature and coercive field. Our estimates of these differences show that the…
Ferromagnetism and Chirality in Two-Dimensional Cyanide-Bridged Bimetallic Compounds
2002
The combination of hexacyanoferrate(III) anions, [Fe(CN)(6)](3)(-), with nickel(II) complexes derived from the chiral ligand trans-cyclohexane-1,2-diamine (trans-chxn) affords the enantiopure layered compounds [Ni(trans-(1S,2S)-chxn)(2)](3)[Fe(CN)(6)](2).2H(2)O (1) and [Ni(trans-(1R,2R)-chxn)(2)](3)[Fe(CN)(6)](2).2H(2)O (2). These chiral systems behave as ferromagnets (T(c) = 13.8 K) with a relatively high coercive field (H(c) = 0.17 T) at 2 K. They also exhibit an unusual magnetic behavior at low temperatures that has been attributed to the dynamics of the magnetic domains in the ordered phase.
Fine–grained spinel ferrites: From the reactivity to magnetic properties
1998
The oxidation at low temperature of fine-grained ferrites containing oxidizable cations such as Cu + , Fe 2+ , Mn 2+ , Mo 3+ , V 3+ , has led to new mixed-valent cation deficient ferrites with a large number of vacancies. It has been demonstrated by DTG analysis that each cation oxidizes at a specific temperature in close relation with the cation-oxygen distance. The kinetics oxidation of each oxidizable cation has been explained on the basis of a diffusion-induced stress effect when these stresses are generated by the chemical gradient induced during the oxidation process. When fine-grained ferrites contain some Co-cations, it has been revealed that the stresses have a significant influenc…
Analysis of the oxidation process and mechanical evolution in nanosized copper spinel ferrites. Role of stresses on the coercivity
1997
Isothermal oxidations of the iron(II) and copper(I) cations in nanosized copper spinel ferrites which were oxidized in cation-deficient spinels have been studied by thermogravimetric analysis. The low temperature kinetics of oxidation of each oxidizable cation has been explained on the basis of a diffusion-induced stress effect, these stresses being generated in the ferrite particles by the chemical gradient induced during the oxidation process where the cations at the surface are more oxidized than those in the bulk. A reaction mechanism coupling the chemical and the mechanical effects has been proposed. When the Cu-ferrites contain some Co-cations, it has also been revealed that the stres…