Search results for "Coercivity"

Peculiarities of Forming of Magnetic Hardening in Sintered Nd15Fe76.2Ti1.0Al0.8B7 Permanent Magnet by Ageing

1999

Variations of the intrinsic coercivity ( i H c ) with ageing (at 293 to 1173 K for 0.45 to 57.6 ks) of sintered Nd 15 Fe 76.2 Ti 1.0 Al 0.8 B 7 have been investigated. The tests indicated minimum and maximum of intrinsic coercivity ( i H min c and i H max c ) at temperatures 725 K and 1025 K, respectively. The observed behaviour of i H c has been compared with microhardness measurements and microstructure observations (SEM, EDAX, domain structure (DS) and room temperature Mossbauer spectroscopy). SEM and DS investigations gave hints to a change in microstructure. Fitting of the Mossbauer spectra of permanent magnets for different i H c has shown that the magnetic hyperfine field Bhf of 8j2 …

The influence of intergranular interaction on the magnetization of the ensemble of oriented Stoner-Wohlfarth nanoparticles

2008

We consider the influence of interparticle interaction on the magnetization reversal in the oriented Stoner-Wohlfarth nanoparticles ensemble. To do so, we solve a kinetic equation for the relaxation of the overall ensemble magnetization to its equilibrium value in some effective mean field. Latter field consists of external magnetic field and interaction mean field proportional to the instantaneous value of above magnetization. We show that the interparticle interaction influences the temperature dependence of a coercive field. This influence manifests itself in the noticeable coercivity at $T>T_{b}$ ($T_{b}$ is so-called blocking temperature). The above interaction can also lead to a forma…

Effect of antisite defects on the magnetic properties of ZnFe2 O4

2013

Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…

Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3

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 SmFeO$_3$. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO$_3$(110) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO$_3$/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 field, suggesting that field-induced canti…

Sintered (Nd, Tb)–(Fe, Ti)–B+C permanent magnets

2001

Abstract This paper undertakes a study of the effect of carbon addition on the magnetic properties, the microstructure and corrosion resistance of Nd14.60Tb0.20Fe77.56Ti1.24B6.40+C sintered permanent magnets. It is shown that a 0.12 wt.% C addition increase the remanence and the maximum energy product and reduces (slightly) the intrinsic coercivity. The corrosion resistance in atmospheric environment is also significantly improved by this element.

New Ceramics for the Information Storage: Nanoparticles of Titanium Ferrites. Influence of Oxidation and Reduction Reactions upon the Coercivity

1997

Structure, micromechanical and magnetic properties of polycarbonate nanocomposites

2013

The current study evaluates the applicability of polycarbonate (PC) for development of magnetic polymer nanocomposites with CoFe2O4 nanofiller, the amount of which was changed from 0 to 5 wt. %. Ethylene-vinyl acetate elastomer in the amount of 10 wt. % was added as toughener. Upon introduction of the magnetic filler a magnetic hysteresis loop was observed: at 5 wt.% of CoFe2O4 saturation magnetization of the nanocomposite was 2,2 emu/g, remanent magnetization was 0,8 emu/g and coercivity is 1200 G. Nanoindentation tests showed that nanofiller-reinforced samples maintain reasonable plasticity characterized by work of plastic indentation, while their modulus and hardness were improved by up …

Synthesis, characterization and functionalization of nearly mono-disperse copper ferrite CuxFe3−xO4 nanoparticles

2011

Magnetic nanocrystals are of great interest for a fundamental understanding of nanomagnetism and for their technological applications. CuxFe3−xO4 nanocrystals (x ≈ 0.32) with sizes ranging between 5 and 7 nm were synthesized starting from Cu(HCOO)2 and Fe(CO)5 using oleic acid and oleylamine as surfactants. The nanocrystals were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), magnetization studies and Mossbauer spectroscopy. The CuxFe3−xO4 particles are superparamagnetic at room temperature 300 K with a saturation magnetization of 30.5 emu g−1. Below their blocking temperature of 60 K, they become ferrimagnetic, and at 5 K they show a co…

Influence of Compressive Stress on Dielectric and Ferroelectric Properties of the(Na0.5Bi0.5)0.7Sr0.3TiO3Ceramics

2013

Good quality lead-free ceramics of (Na0.5Bi0.5)0.7Sr0.3TiO3(NBTS30) have been produced by a solid phase sintering process. The dependence of dielectric and ferroelectric properties on the unaxial pressure (0–1200 bar) were investigated. A shift and decrease of maximum value of e, decrease of the thermal hysteresis and coercive field and increase of polarization with increasing pressure were observed. The results were discussed in terms of an elastic changes in inter-ionic distances in a crystal structure and switching nanoregions under the action of pressure. The NBTS30 ceramic is expected to be a new promising candidate for lead-free electronic material.

The effect of interface roughness on exchange bias in La0.7Sr0.3MnO3 - BiFeO3 heterostructures

2016

We characterized the interfaces of heterostructures with different stack sequences of La0.7Sr0.3MnO3/BiFeO3 (LSMO/BFO) and BFO/LSMO using TEM revealing sharp and rough interfaces, respectively. Magnetometry and magnetoresistance measurements do not show a detectable exchange bias coupling for the multistack with sharp interface. Instead, the heterostructures with rough and chemically intermixed interfaces exhibit a sizable exchange bias coupling. Furthermore, we find a temperature-dependent irreversible magnetization behavior and an exponential decay of coercive and exchange bias field with temperature suggesting a possible spin-glass-like state at the interface of both stacks.