Use Of Magnetometry Research Articles

Structural isomerism-tuned magnetisation relaxation dynamics in lanthanide coordination complexes

Control of the composition of molecular magnetic materials by chemical modification leads to tuning of their magnetization dynamics. We show that two structural isomers display such differences with respect to each other and to their parent complex.

Crystalline texture of cobalt nanowire arrays probed by the switching field distribution and FORC diagrams

The crystalline texture of arrays of low diameter Co nanowires (NWs) synthesized by electrodeposition using electrolytes with different acidities (pH in the range 2.0–6.6) was studied by the switching field distribution (SFD) and first order reversal curve (FORC) diagrams. Particularly, the SFD determined as the derivative of the descending part of the major hysteresis loop has proven to be a reliable and powerful method for the identification of different crystalline textures in the NWs and the quantification of their corresponding texture percentages. The presence of the face centered cubic-like texture at low pH values and hexagonal close packed textures with the c-axis perpendicular and parallel to the NWs axis at higher pH values have been identified by performing multiple Gaussian fits to the SFD by virtue of their different magnetic behavior observed during reversal of the magnetization. The field position and size of each curve in the multiple Gaussian fit provide information about the corresponding magnetic contribution and volumetric texture percentage of each crystalline texture in the NWs, respectively. The analysis of the SFD has been complemented and validated with FORC diagram measurements, showing that the width of the coercive field distribution is in good agreement with the width of the SFD. Also, it has been found that the different branches observed in the FORC diagrams along the interaction axis provide further insight on the interaction between magnetocrystalline fields. This work provides a novel methodology for the use of magnetometry as a reliable technique for the study of the interplay between the microstructure and magnetic behavior of arrays of NWs.

Magnetometric Methods in Archaeology (on the Example of Excavations in Uruk, Iraq): Systematic Literature Review

The article examines various theoretical points of view and concepts that exist in the modern literature on the problem of conceptualization of magnetometry in the aspect of archaeological research. The aim of the article is to characterize magnetometric methods by studying the literature which describes the convergence of magnetometry and archaeological excavation issues, as well as to identify areas for future research developments. In conducting this study, such general scientific methods as a systematic approach, analysis, synthesis, and generalization were used. 72 scientific articles obtained from the results of a bibliographic search in the Scopus and RSCI databases were analyzed. A systematic review of the available scientific literature revealed a limited but rapidly growing coverage of this phenomenon by scientific research, which mainly focused on several aspects: characteristics of magnetometric methods, potential and problems of their use in archaeology; archaeological exploration-magnetic susceptibility studies, magnetometric studies; archaeomagnetic dating. Magnetometric methods are widely used in archaeological research of the city of Uruk and its surroundings. An analysis of the literature has provided insight into the important contribution of the information stored in the magnetic record to the modern archaeology of Uruk. The magnetometer study will continue and provide a comprehensive picture of the Uruk structure over time. Further research efforts to expand the scope of research on the possibilities of using magnetometry in archaeology can be aimed at overcoming a number of problems. The prospects for expanding the use of magnetometry in archaeology are associated with overcoming a number of methodological and technological limitations. Combining the magnetometry data and the results of statistical studies, such as Bayesian statistics, reduces the number of errors of each method and leads to an increase in the accuracy of the results.

Use of magnetometry for detecting and documenting multi-species Pleistocene megafauna tracks at White Sands National Monument, New Mexico, U.S.A

Tracks and trackways of a range of Pleistocene megafauna can be found in White Sands National Monument, New Mexico, U.S.A. These tracks occur is several forms, not all of which are visible and some of which are only intermittently visible depending on lighting and moisture conditions. Here we present the result of a successful test of cesium vapor magnetometry to detect a known Columbian mammoth trackway. This initial test found that not only the known mammoth tracks were easily detected by the method, but that the tracks of additional species, though not visible to the eye, were detected in the vicinity of the mammoth tracks, including likely giant sloth tracks. Our initial results indicate that resolution may be suitable to distinguish between the tracks of various species, including possibly humans which are known archaeologically to have overlapped temporally with these species in the southwestern U.S. This preliminary result has immediate implications for the detection and documentation of Pleistocene track sites, and further refinement of the procedure is planned in the coming months.

Combined use of magnetometry and spectroscopy for identifying magnetofossils in sediments

Identification of the mineral remains of magnetotactic bacteria (MTB), known as magnetofossils, is of particular interest because their occurrence can be used for environmental and climatic reconstructions. Single-domain magnetite particles, which are biomineralized in the cell body of MTB, have characteristic properties that can be used to detect their fossil remains. Acquisition of anhysteretic and isothermal remanent magnetization (ARM and IRM), first-order reversal curve (FORC) diagrams, and ferromagnetic resonance (FMR) spectra were used to detect the magnetic mineral inventory in Holocene lake sediments. A comparative analysis in terms of the discriminatory power of these methods is presented. The FORC diagrams contain two distinct features: a sharp horizontal ridge centered on the horizontal axis Bc and a feature with symmetric spread along the vertical Bb axis. The coercivity spectra derived from the central ridge coincides with that derived from ARM and IRM acquisition curves and is compatible with the presence of noninteracting linear chains of single-domain magnetite. The second feature on FORC diagrams is indicative of interacting particles in clusters. In the FMR spectra from bulk sediment, two populations are separated empirically based on the FORC information. An asymmetric signal is taken to describe the population, which contains single-domain particles in clusters. Empirical spectral separation of this contribution results in FMR spectra that are similar to those of intact MTB, which strongly suggests that a fraction of linear magnetosome chains is present. Combination of FMR and FORC results demonstrates the strong potential of these methods for identifying magnetofossils, based on alignment and interaction patterns of magnetic particles.

The use of magnetometry and pole-dipole resistivity for locating Nabataean Hawar archeological site in the SW-Jordan

This paper is focused on the joint use of magnetometry and pole-dipole electrical resistivity geophysical methods for assessing their capability in the detection of a prehistoric site in the southwestern Jordan. The survey area, Auara, was built in the first century BC during the Nabataean time and is located in a very arid environment framed on the east and north by white sandstone hills. In order to test this site, a number of magnetic stations and two pole-dipole resistivity traverses were carried out in the investigated area. Magnetic data were taken with one sensor at height of 0.8 m along survey lines spaced 1 m apart. Resistivity measurements were carried out utilizing the pole-dipole array along two profiles. A total of 32 geoelectrical stations spaced 2 m were made along the two profiles. Magnetic method found structure with contrasting physical properties to those of the surrounding material. The archeological interpretation of such structure is in terms of rectangular cistern (pool) with dimensions 26 × 16 m. A probable location of two buried walls spaced 16 m are indicated by low resistivity values.

Collective states of interacting ferromagnetic nanoparticles

Discontinuous magnetic multilayers [CoFe/Al 2O 3] are studied by use of magnetometry, susceptometry and numeric simulations. Soft ferromagnetic Co 80Fe 20 nanoparticles are embedded in a diamagnetic insulating a-Al 2O 3 matrix and can be considered as homogeneously magnetized superspins exhibiting randomness of size (viz. moment), position and anisotropy. Lacking intra-particle core-surface ordering, generic freezing processes into collective states rather than individual particle blocking are encountered. With increasing particle density one observes first superspin glass and then superferromagnetic domain state behavior. The phase diagram resembles that of a dilute disordered ferromagnet. Criteria for the identification of the individual phases are given.

Low-noise Nd:LaMgAl11O19 laser for use in magnetometry

A stable, low-noise, tunable, solid-state laser has been constructed for use in magnetometry. The system is designed specifically for applications in which a rugged, magnetically clean source is required. A La1−xNdxMgAl11O19 (LNA or LMA) laser crystal provides the 1083-nm radiation necessary for optical pumping of gaseous helium, the process on which our magnetometer design is based. Laser characteristics of the 0.5-W SDL 2432 laser-diode-pumped device consist of 112-mW free-running laser output near 1082 nm, a threshold of 35 mW, and an output power of up to 26 mW within a single longitudinal mode at the helium metastable resonance wavelengths, obtained by insertion of an intracavity solid étalon. The structure of the ‘‘hand-held’’ laser unit is presented with particular emphasis on the laser parameters required for low-noise operation of this source at the wavelengths of interest.