Previous studies have compiled relative paleointensity data for the last 2–3 Ma from individual paleomagnetic records obtained from marine sediment cores. These records have mostly been obtained by pass-through measurements, which are known to smooth and alter magnetic signals. Among many efforts, a standalone open-use graphical soft- ware UDECON has been developed to deconvolve pass-through measurement data. As an initial case study to assess the applicability of the software to deconvolve naturalremanentmagnetization (NRM) of a continuous paleomag- netic sample, we chose 40 discrete samples from a piston core recovered in the northeast Pacific. We measured NRMs after alternating field demagnetization at 20 mT for both discrete samples and a simulated continuous sample, made by connecting the discrete samples. The discrete samples show centimeter-scale variations in NRM. Such variations are smoothed out and mostly disappear in the results of the simulated continuous sample. However, after using the software to deconvolve the data, the variations are almost completely restored. Good agreement between the discrete sample data and the deconvolved data indicates that the deconvolution by the software is very successful. We observe detailed features of a directional reversal in the data from the discrete samples and in the deconvolved data but not in the data from the simulated continuous sample. This emphasizes that the deconvolution analysis by the software is a powerful tool to extract detailed features from continuous paleomagnetic records obtained by pass- through measurements.
A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 – 1700 A.D. We measured low and high-field magnetic susceptibility, the naturalremanentmagnetization (NRM), saturation isothermal remanentmagnetization (SIRM), and stability against thermal and alternating field (AF) demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1%) during the Medieval Warm Epoch (700–1300 A.D.) than during the Little Ice Age (1300–1850 A.D.) where it is <1%. Diamagnetic behavior has been noted to be prevalent in regions with higher tree ring density. The mineralogical nature of the remanence carrier was not directly detected but maghemite is suggested due to low coercivity and absence of Verwey transition. Tree ring density, along with the wood's magnetic remanence efficiency, records the Little Ice Age (LIA) well documented in Europe. Such a record suggests that the European LIA was a global phenomenon. Magnetic analysis of the thermal stability reveals the blocking temperatures near 200 degree C. This phenomenon suggests that the remanent component in this tree may be thermal in origin and was controlled by local thermal condition.
degree of complexity associated with this process than can be fully accessed by two-dimensional (2D) in-plane representations of magnetization. Comparison between experimental and simulated magnetic induction maps, derived from multiphase three- dimensional (3D) micromagnetic models, could in future elucidate the 3D nature of the transformation observed in these magnetic domain states with chemical oxidation, providing fundamental insight into its effect on magnetic recording ﬁdelity. This combined ETEM and off-axis electron holography investigation has demonstrated changes in both remanent magnetic ﬁeld strength and direction of magnetization within individual PSD particles as a consequence of accelerated chemical oxidation. When averaged over the millions of grains within a bulk palaeomagnetic sample, it is likely that the original directional information will be retained within the palaeo- magnetic sample as not all grains will re-orientate their magnetization, although it is probable that some magnetic moments will re-align with the ambient ﬁeld, giving rise to a CRM contribution to the total remanence. Certainly, the naturalremanentmagnetization intensity of a palaeomagnetic sample will most likely be decreased as a consequence of the oxidation process, resulting in an underestimate of ancient geomagnetic ﬁeld intensity. Accordingly, palaeomagnetic data from samples showing evidence for chemical oxidation should be interpreted with care. The magnetic signal from natural rocks is inherently complex, comprising contributions from a mixture of low coercivity nonuniform MD magnetic grains, magnetically stron- ger nonuniform or vortex state PSD grains, and more stable high coercivity uniformly magnetized SD grains. As a step forward towards a better understanding of palaeomagnetic signals from the geomagnetic record, this study provides fundamental insight into the effect of chemical alteration on magnetic recording ﬁdelity of the strongest magnetic mineral (magnetite) in the most commonly occurring domain state (PSD grains).
Using a direct method, we studied the MCE in La1– xSrxMnO3, Sm0.55Sr0.45MnO3, andPrBaMn2O6 com- pounds, which represent three manganite classes, namely, La1 – xAxMnO3 (A = Ca, Sr, Ba), Sm0.5 + xS0.5 – xMnO3 (0.05 ≤ x ≤ 0.10), and layered ReBaMn2O6 man- ganite. We measured the magnetization of these composi- tions and calculated the MCE related to the change in the magnetic part of entropy induced by a break in the spon- taneous magnetization at the Curie temperature in the firsttwo compositions and by the transition from an AF into an F state at the Néel temperature of the last composi- tion. The calculated value of MCE was found to be sever- al times higher than the absolute value of MCE measured by a direct method. This difference was shown to be re- lated to the presence of AF regions in the manganites with a predominant F order and the presence of F regions in the manganites with a predominant AF order. On the other
metallic with a close packed lattice of iron atoms whose interstices are occupied by nitrogen atoms. It is considered that there exists covalent bonding between the iron atoms and the nitrogen atoms. Thus, fine particles of ferromag- netic iron-nitrides have a potential application to magnetic fluids that need a high magnetization and stability against oxidation.
maximum. 4 It is therefore important for an MTJ to possess a clear two-stage magnetization reversal process for applica- tion purposes. The aim of this work is to directly observe and hence to obtain a better understanding of the magnetization reversal process of NiFe/Al-oxide/Co junction films using Lorentz transmission electron microscopy 共 LTEM 兲 and mag- netic force microscopy 共 MFM 兲 . The successful application of LTEM for the characterization of magnetoresistive multilayer systems has been reported. 5,6 MFM-based tech- niques have been exploited to characterize properties and performance of magnetoresisitive devices such as the effect of shield on magnetoresistive read-head performance 7 and the magnetoresistive response of patterned giant magnetore- sistance sensors with different edge stabilization schemes. 8 The coercivity of NiFe is lower than that of Co, hence it is expected that a two-stage magnetization reversal process can be observed. The magnetic moments in the junction film are believed to be mainly oriented in plane because of the thin- film geometry, therefore, it is very useful to use the LTEM technique to observe the magnetic domains and the reversal process of the junction films, as LTEM is sensitive to in-
A non-destructive evaluation technique for deriving stress in ferromagnetic materials including deriving anhysteretic and hysteresis magnetization curves for the material in both unstressed and stressed states. The anhysteretic curve is expressed as a Langevin function. The stress is expressed as an equivalent magnetic field dependent on stress and change of magnetostriction with magnetization. By measurement of these bulk magnetic properties, stress can be derived.
The - T behaviour of the undeformsd specimen around room temperature may be associated with the diffu sion of carbon atoms* The interstitial carbon atoms redistribute themselves around room temperature and according to Snosk  affect the susceptibility by migrating to Bloch walls. The anomaly at higher tempera ture could be due to vacancy migration. According to Dietze  the energy of a lattice vacancy depends on the direction of magnetization in its immediate neighbor hood • The orientation of magnetization in a Bloch wall changes continuously from one crystallographic preferred direction to another one. This results in an interaction of the vacancies with the Bloch walls. The thermal energy facilitates the diffusion of the vacancies towards the Bloch walls and a new vacancy concentration is established inside the walls, which further hinders the wall movement and causer a drop in above 300°C.
Eﬀects of ultra-strong magnetization in creation of iron group nu- clides are considered by employing arguments of nuclear statistical equilibrium. Nuclear magnetic reactivity is demonstrated to enhance the portion of titanium product due to magnetic modiﬁcation of nu- clear structure. The results are corroborated with an excess of 44 Ti revealed from the Integral mission data.
white color, and black color shows the opposite direction, vice versa. Observed from micro-magnetic- graph, for t < 2 ns, the magnetization dominated by multi domain configuration. During heating process, 2 < t < 3 ns, the random magnetization realized. Whereas for cooling writing process, t > 3 ns, the magnetization re- versal mechanism starts with a domain wall nucleation and continued by domain wall annihilation so that single domain to the H w direction realized.
This paper focuses on various mitigation methods for inrush current in transformers. Current significantly reduces with point on wave switching method. Increasing of the switching angle will decrease the inrush current amplitude. Results show that by increasing switching angle will decrease the inrush current amplitude at a positive remanent flux or source resistance. The effect of remanent flux on the first cycle peak current indicates that it has large changes when the remanent flux varies.
The common method for measuring magnetic properties of samples is to first measure the Anhysteretic Re- manent Magnetization (ARM) before Isothermal RemanentMagnetization (IRM) is induced into the sample . The preference of inducing first ARM revolves around the fact that, ARM is the magnetization which has been left behind in a ferromagnetic material after an external magnetic field is removed. Consequently, the procedure of inducing ARM first and measuring its value using magnetometer then detaching it using an alternating field (a.f) demagnetizer destroys the ARM. This process of demagnetization helps to return the remanence of the sample to zero. In so doing, ARM has been used as a useful laboratory technique for characterizing magnetic properties.
Eddy current testing is a powerful method to test steel plates for cracks and corrosion pits. However, the measurement results from such a scanner appear hard to interpret. During this project it has been tried to ﬁnd a way to improve data abstraction from these measurements. This has been done by creating a model based on a computational technique. The ﬁnite diﬀer- ence time domain (FDTD) technique appeared to be most suitable for this project. This method is especially developed for electromagnetic problems and is relatively easy to understand. By solving Maxwells equations in time, wave propagation can be investigated as well as statical problems. A drawback of the method is the relative big computational load that is required. A model and graphical user interface (GUI) have been built from scratch to get maximum in- sight in the computational technique and to create a dedicated, easy to use model. A single turn coil have been implemented to compare calculated self-inductances to an approximation formula. This way the inﬂuence of the perfectly matched layer (PML) and frequency on the simulation results could be determined. It has also be shown that DC currents in a coil generate correct H-ﬁelds for both true dimensions and down-scaled dimensions. Thereafter the model has been extended with a steel plate and artiﬁcial holes to compare results with measurements. It appeared that the model calculated realistic results in case of plain AC measurements (without an external DC magnetic ﬁeld). Implementation of a magnetization process for the steel plate was less successful, although acceptable results were obtained using only linear magnetization. The magnetization process have to be improved before reliable comparisons with measurements can be made.
The value of coercivity first increases from 1877Oe at X=0 and reached the maximum value of 2348Oe at X=0.1 and then drops drastically at 1164Oe at x=0.5. The Nb-Zn doped with Ba-Sr hexaferrite with X up to 0.5 resulted in the reduction of coercivity and improved saturation and remanence magnetization at relatively high level suitable for high density magnetic recording applications. The Fe 3+ ions in M-type hexaferrite structure are distributed on ﬁve different crystallographic sites such as three octahedral (2a, 12k and 4f 2 ), one tetrahedral (4f 1 ) and one trigonal bipyramidal (2b)
Characterization of magnetic properties is one of the key issues for development of future magnetic and spintronic devices. The dimension and the operation frequency of those devices has reached nanoscale and GHz regime, respectively, so that it is required to realize new measure- ment technique with such sensitivity and time resolutions. The anomalous Hall effect (AHE) can be adopted as a probe capable to approach magnetization behavior in nanoscale structure. We have developed AHE measurement technique for nanostructure and investigated magnetiza- tion reversal behavior of perpendicularly magnetized dot in dynamic field. In this article, we overview the capability of AHE measurement as a probe for magnetic characterization and the experimental results of magnetization behavior of Co/Pt multilayer dots in pulse fields with nano- seconds durations.[doi:10.2320/matertrans.ME201507]
scale ferrite particles can be synthesized by using solution combustion method. As the combustion process involves exothermic reaction and a large amount of heat is released, the ferrites can be synthesized at lower temperature. X- ray diffraction studies reveal the formation of single phase spinel structure. Magnetic studies show variation of coercivity and saturation magnetization with cobalt substitution and show higher coercivity and saturation magnetization than pure nickel ferrites. From the Mössbauer recording, presence of two well resolved Zeeman sextets, which is due to Fe 3+ ions distribution in tetrahedral and octahedral sites, ferrimagnetic nature of ferrite materials is revealed.
The crystal structure was determined by X-ray diffrac- tion (XRD) spectrum using a Rigaku D/max 2200 X-ray diffractometer (Rigaku Corporation, Tokyo, Japan) with Cu-Kα radiation. Morphological characterization was observed using a field emission scanning electron micro- scope (FE-SEM, JEOL JSM-6700 F, JEOL Ltd., Akishima, Tokyo, Japan) at 3.0 kV. Secondary ion mass spectrom- etry (SIMS) was utilized to identify the elemental distri- bution. Room temperature photoluminescence (RTPL) spectroscope was used to measure optical emissions from 350 to 645 nm using the He-Cd laser with wave- length of 325 nm. Raman spectra of the samples were measured with an excitation wavelength of 532 nm from argon laser. Finally, the magnetization measurements were performed using a MicroMag™ 2900 alternative gradient magnetometer (AGM) (Princeton Measure- ments Corp., Princeton, NJ, USA) at room temperature to investigate the magnetic properties of ZnO and ZnO: Y nanorods.