共查询到20条相似文献,搜索用时 15 毫秒
1.
In situ magnetic hysteresis measurements of magnetic tips in a magnetic force microscope (MFM) are demonstrated using alternating gradient force magnetometry. The measured magnetic moments of MFM tips are estimated in the range from 10−6 to 10−5 emu by this technique and the whole MFM tips in cantilevers are considered to be measured from the value of measured magnetic moments. The relationship between the magnetic hysteresis loops of MFM tips and those of coated magnetic films is discussed. 相似文献
2.
A new ferromagnetic hysteresis model for soft magnetic composite materials based on their specific properties is presented. The model relies on definition of new anhysteretic magnetization based on the Cauchy-Lorentz distribution describing the maximum energy state of magnetic moments in material. Specific properties of soft magnetic composite materials (SMC) such as the presence of the bonding material, different sizes and shapes of the Fe particles, level of homogeneity of the Fe particles at the end of the SMC product treatment, and achieved overall material density during compression, are incorporated in both the anhysteretic differential magnetization susceptibility and the irreversible differential magnetization susceptibility. Together they form the total differential magnetization susceptibility that defines the new ferromagnetic hysteresis model. Genetic algorithms are used to determine the optimal values of the proposed model parameters. The simulated results show good agreement with the measured results. 相似文献
3.
V. I. Kamenev K. V. Kamenev B. M. Todris E. A. Zavadskii V. N. Varyukhin N. V. Baranov 《高压研究》2013,33(1-2):195-199
The effect of high pressure and magnetic field on the stability of magnetic phase transitions in (Fe1?x Ni x )49Rh51 has been studied. It has been shown that the increase in the Ni content suppresses the stability of the low-temperature antiferromagnetic phase and leads to its disappearance. Pressure on the other hand restores the stability to the antiferromagnetic order. These findings are explained using first-principles band-structure calculations. 相似文献
4.
《Physics letters. A》2019,383(31):125878
Elements of alnico 8 are added into Nd-Fe-B alloys fabricated by rapid solidification method. It is observed that the magnetic properties at high temperature improved by small addition of alnico elements. The Curie temperature of the alloys increased from 580 K for standard alloy to 639 K by 20% addition of alnico 8 elements. The spin reorientation temperature decreased from 133 K to 104 K. The TEM analysis showed that elements of alnico 8 refine the microstructure of Nd-Fe-B ribbons. The STEM analysis confirmed the heterogeneous distribution of Nd, Fe, Cu, Al, Ni and homogeneous distribution of Ti, Nb and Co. The boundaries of nano grains contain more than 70% ferromagnetic elements, ensuring strong inter-grain coupling among the grains. 相似文献
5.
J. Escrig P. Landeros D. Altbir E.E. Vogel P. Vargas 《Journal of magnetism and magnetic materials》2007
Analytical expressions for the total magnetic energy of two characteristic internal configurations of nanometric tubes are calculated. A magnetic phase diagram with respect to the aspect ratio of the tubes is obtained which allows a discussion about the possibility of getting ensembles of nanotubes with low coercive fields. A comparison with recently reported coercive fields of three different cobalt nanotube arrays agrees well with the phase diagram derived here. 相似文献
6.
Data compressors available in the web have been used to determine magnetic phases for two-dimensional (2D) systems [E. Vogel, G. Saravia, F. Bachmann, B. Fierro, J. Fischer, Phase transitions in Edwards-Anderson model by means of information theory, Physica A 388 2009 4075-4082]. In the present work, we push this line forward along four different directions. First, the compressor itself: we design a new data compressor, named wlzip, optimized for the recognition of information having physical (or scientific) information instead of the random digital information usually compressed. Second, for the first time we extend the data compression analysis to the 3D Ising ferromagnetic model using wlzip. Third, we discuss the tuning possibilities of wlzip in terms of the number of digits considered in the compression to yield maximum definition; in this way, the transition temperature of both 2D and 3D Ising ferromagnets can be reported with very good resolution. Fourth, the extension of the time window through which the data file is actually compressed is also considered to get optimum accuracy. The paper is focused on the new compressor, its algorithm in general and the way to apply it. Advantages and disadvantages of wlzip are discussed. Toward the end, we mention other possible applications of this technique to recognize stable and unstable regimes in the evolution of variables in meteorology (such as pollution content or atmospheric pressure), biology (blood pressure) and econophysics (prices of the stock market). 相似文献
7.
Rare earths exhibit complex magnetic phase diagrams resulting from the competition between various contributions to the magnetic
energy: exchange, anisotropy and magnetostriction. The epitaxy of a rare-earth film on a substrate induces (i) a clamping
to the substrate and (ii) pseudomorphic strains. Both these effects are shown to lead to modifications of the magnetic properties
in (0 0 1)Dy, (0 0 1)Tb and (1 1 0)Eu films. In Dy and Tb films, spectacular variations of the Curie temperature have been
evidenced. Additionally, Tb films exhibit a new large wavelength magnetic modulation. In Eu films, one of the helical magnetic
domains disappears at low temperature whereas the propagation vectors of the other helices are tilted. The link between structural
and magnetic properties is underlined via magnetoelastic models. Moreover, molecular beam epitaxy permits the growth of Sm
in a metastable dhcp phase. The magnetic structure of dhcp Sm has been elucidated for the first time. In this review, neutron
scattering is shown to be a powerful technique to reveal the magnetic structures of rare-earth films. 相似文献
8.
V.A. Naletova V.A. TurkovD.A. Pelevina A.V. RozinK. Zimmermann J. PoppI. Zeidis 《Journal of magnetism and magnetic materials》2012,324(6):1253-1257
The deformation of the free surface of a magnetic fluid containing a cylinder made of a magnetizable material subjected to a uniform applied magnetic field is analyzed. The statics and dynamics of a magnetic fluid free surface is studied theoretically and experimentally. A discontinuous (jump-like) change of the surface shape is shown to occur when the applied magnetic field gradually increases or decreases. If the applied magnetic field increases and then decreases, a hysteresis of the shape is observed. 相似文献
9.
J.A. Gonzalez L.-A. Michez T.R. Charlton B.J. HickeyS. Langridge C.H. Marrows 《Physica B: Condensed Matter》2011,406(13):2689-2696
We report the measurement of reflected neutron intensity “hysteresis loops” from Co/Ru multilayers that have both antiferromagnetically and ferromagnetically coupled regions. We show that by measuring the four neutron spin-resolved reflectivities at a particular value of wavevector transfer, the normalised value of the relevant magnetic order parameter may be determined. The response of that order parameter to an applied magnetic field may hence be tracked. We have benchmarked our results against conventional magnetometry and magnetotransport measurements. 相似文献
10.
G.C. DeFotis T.M. Owens W.M. May J.H. Boyle E.S. Vos Y. Matsuyama A.T. Hopkinson T.J. Wallin E.A. Welshhans 《Journal of magnetism and magnetic materials》2010,322(14):1962-1968
A new mixed magnet, Mn1−xNixCl2·H2O, is examined by dc magnetization and susceptibility measurements across the entire composition range. The pure components are quasi-one-dimensional Heisenberg antiferromagnets ordering at 2.17 K (Mn) and 5.65 K (Ni) due to weaker interchain exchange supplementing the dominant exchange along MCl2MCl2M… chemical and structural chains. High temperature magnetic susceptibilities yield Curie and Weiss constants in χM=C/(T−θ). C(x) is linear but θ(x) displays curvature, which is analyzed to show that unlike-ion exchange is ferromagnetic and similar in size to like-ion. Most notable is the absence of antiferromagnetic susceptibility maxima down to 1.6 K from x=0.10 to 0.95. For x=0.05 a susceptibility maximum appears, with Tmax almost 20% lower than in the pure Mn component but Tc reduced by 2%. The size of the susceptibility is enhanced by admixture, the effect of disrupted antiferromagnetic tendencies. Magnetization isotherms evolve with composition. Larger values of magnetization, under the same measuring conditions, occur for mixtures than for pure components, consistent with frustration, which weakens antiferromagnetic alignment tendencies. The competing ferromagnetic (Ni) and antiferromagnetic (Mn) intrachain interactions, along with disorder and low dimensional characteristics, presumably lead to the absence of magnetic order over a remarkably broad composition range. 相似文献
11.
R.K. Singh M. Manivel RajaR.P. Mathur M. Shamsuddin 《Journal of magnetism and magnetic materials》2011,323(5):574-578
The influence of Fe additions on the martensitic transformation and magnetic properties of Mn-rich Ni-Mn-Ga alloys was investigated by substituting either 1 at% Fe for each atomic species or by substituting Ni with varying amounts of Fe. The magnetic structure of the alloys was studied using 57Fe Mössbauer spectroscopy. Mössbauer spectra revealed typical paramagnetic features in Mn-rich Ni-Mn-Ga-Fe alloys owing to the preferential site occupancy of Fe atoms at Ni sites. The evolution of the magnetic properties and phase stability has been correlated with the chemical and atomic ordering in these alloys. 相似文献
12.
Robert Müller Silvio DutzTobias Habisreuther Matthias Zeisberger 《Journal of magnetism and magnetic materials》2011,323(10):1223-1227
Magnetic iron oxide nanoparticles are promising tools for medical applications like hyperthermia or magnetic drug targeting. The relevant properties in these applications strongly depend on particle size and size distribution. In order to investigate the influence of mean size as well as size distribution, iron oxide powders from particles by a cyclic method based on “conventional” precipitation from Fe-salt solution were prepared. Increasing mean particle size with increasing number of cycles is confirmed by XRD. Magnetic parameters of the saturation hysteresis loop, hysteresis losses calculated from minor loops and switching field distributions are shown. A fractionation experiment on a fluid sample of particles prepared by 3 cycles was carried out in order to improve the hysteresis losses. 相似文献
13.
Xuezhi Zhou Henry Kunkel Gwyn Williams Shuihe Zhang Xue Desheng 《Journal of magnetism and magnetic materials》2006
In Mn rich polycrystalline Heusler alloys, Ni50Mn25+−xGa25−x, prepared by Arc melting, it is found that the structural/first-order magnetic transition temperature Tm increases as the Mn content increases. The Curie temperature Tc is higher than that of Ni rich alloys (Ni50+xMn25−xGa25 ) of the same series, and is less affected by composition x. Magnetic entropy change of |ΔSM| also increases as Mn content increases, while behaviour of the field dependence of ΔSM is similar to that of single crystal Ni52.6Mn23.1Ga24.3. 相似文献
14.
Ultrafine particles (UFP) of six kinds of Fe---Ni alloys were synthesized by the method of hydrogen plasma reaction. The prepared UFP samples were examined by X-ray diffraction, electron transmission microscopy and magnetic measurement. The spherical Fe---Ni UFP alloys with a mean particle size less than 35 nm can be prepared with a production rate much higher than by conventional methods. The phase constitution of UFP alloys is different from the equilibrium phase diagram owing to rapid condensation of evaporated metal gases. Although the magnetization for the UFP alloys has almost the same temperature dependence as that of the bulk alloys, the saturation magnetization remarkably decreases as the bulk alloys change into the UFP alloys. 相似文献
15.
Silvio Dutz Wilfried Andrä Rudolf Hergt Robert Müller Christiane Oestreich Christopher Schmidt Jorg Töpfer Matthias Zeisberger Matthias E. Bellemann 《Journal of magnetism and magnetic materials》2007
Magnetic iron oxide nanoparticles with mean diameters in the range from 10 to 30 nm were prepared by modified chemical precipitation routes. The particles were suspended in an aqueous solution by coating of the particles with carboxymethyldextran. A stability against agglomeration was achieved over a period of more than 7 days. In the present investigation, the structural and the magnetic properties of the nanoparticles were investigated. The influence of the dextran shell on the strength of the dipole–dipole interactions between the neighbouring particles was determined by investigation of the remanence behaviour (Henkel plot) of coated as well as of uncoated particles. 相似文献
16.
Silvio Dutz Joachim H. Clement Thorsten Gelbrich Robert Müller Matthias Zeisberger 《Journal of magnetism and magnetic materials》2009,321(10):1501-1504
For a variety of magnetically based biomedical applications, it is advantageous to use sedimentation stable suspensions of relatively large (d>20 nm) magnetic core-shell nanoparticles. Water-based suspensions of multicore nanoparticles were prepared by coating of the particles (synthesized by means of a modified alkaline precipitation method) with a carboxymethyldextran shell. The resulting ferrofluids were structurally and magnetically characterized. It was found that these fluids show a specific heating power of about 60 W/g (f=400 kHz, H=10 kA/m). This value was increased up to 330 W/g by a simple fractionation method based on centrifugation. Finally, the cellular uptake of the multicore nanoparticles was demonstrated. 相似文献
17.
High-pass filtering is required for the removal of background field inhomogeneities in magnetic resonance phase images. This high-pass filtering smooths across boundaries between areas with large differences in phase. The most prominent boundary is the surface of the brain where areas with large phase values inside the brain are located close to areas outside the brain where the phase is, on average, zero. Cortical areas, which are of great interest in brain MRI, are therefore often degraded by high-pass filtering. Here, we propose the use of the bilateral filter for the high-pass filtering step. The bilateral filter is essentially a Gaussian filter that stops smoothing at boundaries. We show that the bilateral filter improves image quality at the brain's surface, without sacrificing contrast within the brain. 相似文献
18.
Ultrafine particles (UFP) of six kinds of FeNi alloys were synthesized by the method of hydrogen plasma reaction. The prepared UFP samples were examined by X-ray diffraction, electron transmission microscopy and magnetic measurement. The spherical FeNi UFP alloys with a mean particle size less than 35 nm can be prepared with a production rate much higher than by conventional methods. The phase constitution of UFP alloys is different from the equilibrium phase diagram owing to rapid condensation of evaporated metal gases. Although the magnetization for the UFP alloys has almost the same temperature dependence as that of the bulk alloys, the saturation magnetization remarkably decreases as the bulk alloys change into the UFP alloys. 相似文献
19.
20.
B.M. Zawilski J. Marcus P. Plaindoux 《Journal of magnetism and magnetic materials》2010,322(18):2786-2788
Investigation of relative AC magnetic susceptibility interests for many magnetic transition studies such as superconductor transition. A technique based on mutual or self inductive measure provides a fast and relatively easy (no contact) way to determinate the temperature of any transition affecting the magnetic susceptibility. The half Wheatstone inductive/resistive bridge is used instead of the usual RLC quarter bridge in order to balance the bore inductance of the coil. A comparison between quarter and half bridge measurements illustrates the accuracy of our device. 相似文献