Search results for "rema"
showing 10 items of 911 documents
Relaxation of remnant magnetisation in YBa2Cu3O7−δ films
2007
Abstract The relaxation of the remnant magnetisation in optimally doped disk-shaped YBa2Cu3O7−δ films with the initially applied magnetic field H oriented along the c axis was measured using dc SQUID magnetometry. The temperature (T) dependence of the experimentally observed normalised magnetisation relaxation rate S exhibits three distinct regions. At high T, S(T) increases with increasing T, which can be explained in terms of plastic vortex creep. The well known plateau in the S(T) variation at intermediate T appears to be caused by collective (elastic) creep in a dynamically ordered vortex system. At low T, where S increases again with increasing T, the magnetisation relaxation is not in…
Temperature Dependence of Irradiation-Induced Magnetic Flux Loss in Nd 2 Fe 14 B Permanent Magnets
1990
Nd2Fe14B permanent magnets were irradiated with 20 MeV protons at 300 K and at 15 K, and the flux loss was measured as a function of the irradiation dose. The results show that at 15 K the Nd2Fe14B magnets can withstand particle radiation at least 1000 times more than at room temperature.
Polarized neutron reflectivity from monolayers of self-assembled magnetic nanoparticles
2015
We prepared monolayers of iron oxide nanoparticles via self-assembly on a bare silicon wafer and on a vanadium film sputter deposited onto a plane sapphire substrate. The magnetic configuration of nanoparticles in such a dense assembly was investigated by polarized neutron reflectivity. A theoretical model fit shows that the magnetic moments of nanoparticles form quasi domain-like configurations at remanence. This is attributed to the dipolar coupling amongst the nanoparticles.
Coarsening of Antiferromagnetic Domains in Multilayers: The Key Role of Magnetocrystalline Anisotropy
2002
The domain structure of an antiferromagnetic superlattice is studied. Synchrotron Mössbauer and polarized neutron reflectometric maps show micrometer-size primary domain formation as the external field decreases from saturation to remanence. A secondary domain state consisting mainly of at least 1 order of magnitude larger domains is created when a small field along the layer magnetizations induces a bulk-spin-flop transition. The domain-size distribution is reproducibly dependent on the magnetic prehistory. The condition for domain coarsening is shown to be the equilibrium of the external field energy with the anisotropy energy.
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.
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 …
The effect of less additives on magnetic properties and microstructure of sintered Nd–(Fe,Ti,Al)–B magnets
2001
Abstract The effect of the addition of 0.5 at.% Cu, Ga, Hf, V, Mo, Nb, Co, Ni, Cr, Dy or Tb on the magnetic properties and the microstructure of sintered Nd 16 Fe 75.22 Ti 1.26 Al 0.32 B 7.2 magnets has been studied. It is shown that these additives cause a small decrease in remanence and in intrinsic coercivity, with the exception of Cu, Dy and Tb additives, which lead to an increase in the intrinsic coercivity. The correlation between the hyperfine magnetic field and the magnetic properties of the investigated magnets is discussed.
Magnetic properties of Cd–Mg–Tb quasicrystal
2004
Abstract The magnetic properties of an icosahedral Cd–Mg–Tb quasicrystal were studied by dc magnetization and thermoremanent magnetization time decay measurements. An unusual temperature dependence of the susceptibility below freezing temperature can be attributed to the inhomogeneous sample structure. In addition to the quasicrystalline portion which exhibits a spin-glass transition at 12.5 K a part of the sample behaves like a paramagnet. During aging of the sample in air the spin-glass part transforms into the paramagnetic one. The linear M ∝ H dependence of the thermoremanent magnetization time decay on magnetic field is quite different as compared to canonical spin glasses.
Properties of sintered Al substituted NdFeB magnets
1998
The effect of partial substitution of Fe by Al (Al, Al 2 O 3) on the magnetic properties and the corrosion resistance of the sintered NdFeB magnet has been investigated. With the increasing amount of Al, the anisotropy field and the saturation magnetization decrease, but the coercivity increases up to 4 at.% Al and further alloying of Al leads to a decrease of the coercivity. Different substances like Al (metallic Al or Al 2 O 3) modify the microstructure to different increase in the coercivity and especially to changes in the remanence. Alloying Al via metallic Al decreases the remanence, whereas via Al 2 O 3) up to 4 at.%0 Al increases it. The Al additions inhibit atmospheric corrosion o…
Generalized evolutes, vertices and conformal invariants of curves in Rn + 1
1999
Abstract We define the generalized evolute of a curve in ( n + 1)-space and find a duality relation between them. We also prove that the conformal torsion is a function of the speed of the generalized evolute and that the singular points of the generalized evolute (vertices) are conformal invariants.