First-order reversal curve (FORC) measurements are broadly used for the characterization of complex magnetic nanostructures, but they can be inconclusive when quantifying the amount of different magnetic phases present in a sample. In this paper, we first establish a framework for extracting quantitative parameters from FORC measurements conducted on samples composed of a single type of magnetic nanostructure to interpret their magnetic properties. We then generalize our framework for the quantitative characterization of samples that are composed of 2–4 types of FeCo magnetic nanowires to determine the most reliable and reproducible parameters for a detailed analysis of samples. Finally, we conclude that the parameter with the best quantification potential, backfield remanence coercivity, does not require the full FORC measurement. Our approach provides an insightful path for fast, quantitative analysis of complex magnetic nanostructures, especially determination of the ratios of magnetic subcomponents present in multi-phase samples.
- Award ID(s):
- 2005108
- NSF-PAR ID:
- 10436133
- Date Published:
- Journal Name:
- APL Materials
- Volume:
- 10
- Issue:
- 11
- ISSN:
- 2166-532X
- Page Range / eLocation ID:
- 111105
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
SUMMARY Quaternary lavas of the Stardalur Caldera, 20 km northeast of Reykjavik, Iceland, create a 27 300 nT magnetic anomaly visible in both ground and aeromagnetic surveys. Here, we provide a comprehensive mineralogical and rock magnetic data set to analyse NRM intensities and Koenigsberger ratios of 57 drill-core samples from the critical zone (CZ) of the anomaly high at depths between 41 and 131 m. This extends previous studies and verifies that the anomaly is due to an unusually high intensity of remanent magnetization carried by magnetite. The NRM of the CZ samples was acquired during the Olduvai subchron in a field of at most today’s strength. NRM intensities range from 20 to 128 A m–1 with a median of 55 A m–1, and an average of 61 A m–1, respectively, approximately 13–15 times higher than in typical Icelandic basalts (AIB) with an NRM intensity of 4 A m–1. Our new data set shows that the magnetite concentration throughout the CZ basalts is at most twofold higher than in AIB lavas. New data on domain state and TRM efficiency prove that these properties account for an additional factor of at most 2.3. Because magnetite is the most abundant remanence carrier in rocks on Earth, and its remanence acquisition is considered to be extremely well understood, we assert that the remaining discrepancy is a critical enigma in rock magnetism. Results from scanning electron microscopy show that a significant fraction of all CZ magnetite particles have dendritic shapes with grain sizes <1 μm, indicating rapid crystallization. Most large magnetite grains are heavily subdivided by very fine oxidation-exsolution lamellae of ilmenite, and subordinate amount of exsolved spinel as needles, blebs and blades. These common microstructures found throughout the CZ subdivide the initially homogeneous mineral into separate cubicles, here denoted as compartments. The magnetite compartments then have sizes below 1 μm. Hysteresis data, Preisach maps and FORC data consistently confirm that the coercivity distribution is dominated by values above 10 mT, such that multidomain behaviour is of little relevance in the CZ. Between 5 and 20 per cent of the IRM is carried by coercivities above 100 mT, which for magnetite indicates unusually high anisotropy effects in the individual particles. Based on the quantitative analysis of all magnetic contributions to the NRM, we can demonstrate that the average efficiency of NRM acquisition in the CZ Stardalur basalts must be at least a factor 3 higher than in typical basalts. We speculate that this is related to the observed focused compartment size distribution <1 μm, and indicates thermochemical remanence acquisition below the Curie temperature of magnetite. Yet, a detailed physical mechanism for the extreme overefficiency of NRM acquisition remains enigmatic.
-
null (Ed.)Abstract Magnetic nanoparticles have been proposed as contact-free minimal-background nanobarcodes, and yet it has been difficult to rapidly and reliably decode them in an assembly. Here, high aspect ratio nanoparticles, or magnetic nanowires (MNWs), are characterized using first-order reversal curves (FORC) to investigate quantitative decoding. We have synthesized four types of nanowires (differing in diameter) that might be used for barcoding, and identified four possible “signature” functions that might be used to quickly distinguish them. To test this, we have measured the signatures of several combination samples containing two or four different MNW types, and fit them to linear combinations of the individual type signatures to determine the volume ratios of the types. We find that the signature which determines the ratios most accurately involves only the slope of each FORC at its reversal field, which requires only 2–4 data points per FORC curve, reducing the measurement time by a factor of 10 to 50 compared to measuring the full FORC.more » « less
-
SUMMARY Greigite is a sensitive environmental indicator and occurs commonly in nature as magnetostatically interacting framboids. Until now only the magnetic response of isolated non-interacting greigite particles have been modelled micromagnetically. We present here hysteresis and first-order reversal curve (FORC) simulations for framboidal greigite (Fe3S4), and compare results to those for isolated particles of a similar size. We demonstrate that these magnetostatic interactions alter significantly the framboid FORC response compared to isolated particles, which makes the magnetic response similar to that of much larger (multidomain) grains. We also demonstrate that framboidal signals plot in different regions of a FORC diagram, which facilitates differentiation between framboidal and isolated grain signals. Given that large greigite crystals are rarely observed in microscopy studies of natural samples, we suggest that identification of multidomain-like FORC signals in samples known to contain abundant greigite could be interpreted as evidence for framboidal greigite.more » « less
-
Diesel sprays present a challenging environment for detailed quantitative measurement of the liquid field, and to date, there have been only a few efforts to characterize drop sizes within the family of Engine Combustion Network (ECN) diesel sprays. Drop sizing diagnostics, including optical microscopy and Ultra-Small Angle X-ray Scattering (USAXS), have been recently demonstrated in Spray A/D ECN activities, but little data exist to validate these results. This work therefore seeks to extend the available ECN data on the liquid phase field and provide a new comparative data set for assessment of previous ECN drop sizing measurements. In particular, this work presents the development of a two-wavelength, line-of-sight extinction measurement to examine liquid volume fraction and the corresponding droplet field in high-pressure fuel sprays. Here, extinction of lasers emitting at 10.6 μm and 0.633 μm are used for the measurement. To enable quantification of the liquid field in optically dense regions of the spray, a transfer function is developed to account for the influence of multiple scattering. The developed diagnostic is then applied to n-dodecane sprays from the ECN Spray A and Spray D injectors at varying fuel rail pressures and atmospheric chamber condition. Overall, the results show a reasonable agreement with droplet sizes measured using USAXS, as well as from more recent measurements using a Scattering-Absorption Measurement Ratio (SAMR) technique also developed in our group. This is particularly the case near the spray periphery, where on average, less than 40% difference in the measured Sauter mean diameter is observed. Nonetheless, an apparent discrepancy is observed between drop sizes from different diagnostics close to the jet centerline (i.e. nearly 100% difference between available data for Spray D injector). Moreover, the presented diagnostic shows an improved capability in the dilute regions of the spray, where x-ray-based diagnostics are generally subject to high noise and low signal sensitivity.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0122923
