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Pulsed Magnetic Measurements & Pulse Analyses

Pulse measurements & Analyses include:

o Waveform measurement & recording
o Pulse Measurement (RMS, voltage, or RMS Peak)
o Digitized Triggering (Rising or Falling edges)
o Pulse timing durations
o Frequency measurements
o True Magnetic Peak measurements

Coercivity

The Coercivity, also called coercive field or coercive force, is defined in a ferromagnetic material as the value of the applied external magnetic field to reduce the magnetization of a material (or sample) to zero after the sample has been magnetized to saturation. The magnetic parameter of Coercivity is a measure the resistance of a ferromagnetic material to becoming demagnetized.

ARkival measures the coercivity of magnetic material from a magnetic hysteresis loop measured with a vibrating-sample magnetometer (VSM). Coercivity is measured and reported in Oersted or ampere/meter units and denoted by Hc in the Hysteresis loop. In the VSM measurement, the coercivity Hc is measured by applying a (reverse) magnetic field  to reduce the sample magnetization to zero after the samples has been magnetized to saturation. Coercivity is defined from a Hysteresis loop at the point where H Field has a value at “0”. Ferromagnetic materials with high coercivity are called magnetically hard, and materials with low coercivity are said to be magnetically soft.

Torque Measurements

ARkival’s Torque Measurements are performed with a MicroSense VSM employing an ultra-low friction, air bearing suspending the sample with virtually zero friction. The resulting torque measurement reports the actual force on the sample. All pre-measurement calibrations are directly based upon a known torque sample. ARkival’s magnetic torque measurements can accommodate solid, bulk, and thin film samples with a torque measurement capability from 0.05 dyne-cm to 500 dyne-cm depending upon the sample magnetics, applied field, sample type and size.

Direct Magnetic torque measurements can, in some samples be more sensitive than SQUID magnetometry as our direct torque measurement is more precise and more sensitive than an indirect vector coil-based torque system.

Whereas torque is a measure of the sample’s magnetic or shape anisotropy, the magnetic torque measurement can detect magnetic phase transitions or quantum oscillations. Under certain conditions, the sample magnetization can also be extracted from the measured torque.

Permeability, Relative Permeability and Susceptibility

Note: magnetic parameters Magnetizing Force (H) and Flux density (B) used for Permeability measurements

Permeability is the measure of the resistance of a material against the formation of a magnetic field. It is a measure  of the magnetization that a material obtains in response to an applied magnetic field. Magnetic permeability is typically represented by the Greek letter μ. In general, permeability is not a constant value, as it can vary with the position in the medium, the frequency of the applied magnetic field, humidity, temperature, and other criteria. In a nonlinear medium, the permeability can depend on the strength of the magnetic field. Permeability as a function of frequency also addresses real or complex values.

A closely related property of materials is magnetic susceptibility, which is a dimensionless proportionality factor that indicates the degree of magnetization of a material in response to an applied magnetic field.

About Permeability Units

In SI units, permeability is measured in henries per meter (H/m), or equivalently in newtons per ampere squared (N⋅A−2). The permeability constant μ0, also known as the magnetic constant or the permeability of free space, is a measure of the amount of resistance encountered when forming a magnetic field in a classical vacuum.

Until 20 May 2019, the magnetic constant had the exact (defined) value μ0 = 4π × 10−7 H/m ≈ 12.57×10−7 H/m.

On 20 May 2019, a revision to the SI system went into effect, making the vacuum permeability no longer a constant but rather a value that needs to be determined experimentally; 4π × 1.00000000082(20)×10−7 H⋅m−1 is a recently measured value in the new system. It is proportional to the dimensionless fine-structure constant with no other dependencies.

In 2019, the SI base units were redefined in agreement with the International System of Quantities, effective on the 144th anniversary of the Metre Convention, 20 May 2019. In the redefinition, four of the seven SI base units – the kilogram, ampere, kelvin, and mole – were redefined by setting exact numerical values for the Planck constant, the elementary electric charge, the Boltzmann constant, and the Avogadro constant, respectively.

In electromagnetism, the auxiliary magnetic field H represents how a magnetic field B influences the organization of magnetic dipoles in a given medium, including dipole migration and magnetic dipole reorientation. Its relation to permeability is

where the permeability, μ, is a scalar if the medium is isotropic or a second rank tensor for an anisotropic medium.

Relative permeability and magnetic susceptibility 

Relative permeability, denoted by the symbol  , is the ratio of the permeability of a specific medium to the permeability of free space μ0:

 4π × 10−7 N⋅A−2 is the magnetic permeability of free space.

In terms of relative permeability, the magnetic susceptibility is

The number χm is a dimensionless quantity, sometimes called volumetric or bulk susceptibility, to distinguish it from χp (magnetic mass or specific susceptibility) and χM (molar or molar mass susceptibility).

Demagnetization

Demagnetization is a procedure or method used to eliminate unwanted (major or minor) magnetic fields. Demagnetization is also the reduction or elimination of magnetization. The demagnetization procedure can be performed as an automated process done in a VSM to remove residual magnetization resulting from substrate materials, magnetic artifacts, magnetic noise and exchange interactions and the like. The process results in a clearly differentiated ‘before and after’ Hysteresis loop measurement report.

Alternative means to perform demagnetization are to heat the object above its Curie temperature, where thermal fluctuations have enough energy to overcome exchange interactions, the source of ferromagnetic order, and can destroy that order. In some applications and materials an electric coil with alternating current running through it, can also be used to generate alternating magnetic fields that oppose the magnetization.

AC Magnetic Fields

AC Magnetics

AC magnetic measurements provide important property data that supplements DC magnetic data. Low AC field frequency results in an induced AC moment that follows the slope of the DC, B-H/ Hystersis loop curve. A typical reported parameter is AC “susceptibility” and in DC magnetics terminology, reported as the sample permeability.

ARkival uses the newest technology and probes for magnetic field measurements (InAs and GaAs Hall Sensor probes, 2 Dex probes and ARkival’s miniature coil probes) for all AC and DC magnetic measurements. ARkival also employs precision DC magnetometers and AC susceptometers for measuring magnetic materials properties. All probe and meter devices focus on the measurement of magnetic flux (Moment) associated with magnetized samples and fields.

The resulting combination of both AC and DC material properties as reported parameters provides an ideal “fingerprint” of any material and its potential use for different magnetic product applications.

AC Magnetic Field Measurements

ARkival Technology has developed a fast and accurate measurement means for measuring AC magnetic fields and their corresponding AC frequencies in/for magnetic devices. Using both precision Hall probe and Miniature Coil probe access, AC field measurements are made with calibrated accuracy referenced to standardized sources and calibration materials. AC Field measurements can be performed in either 1D,  2D or 3D modes at specific measurement location(s) or over larger areal regions of interest by employing either precision manual testing or automated robotic testing, both with and without optional magnetic field mapping technology.

ARkival’s focus on the accurate measurement of AC material properties uses precision magnetometers that typically limits the material sample size to “small” rather than “large” . In many cases, test samples must be prepared for analysis and sample preparation options are discussed with clients prior to measurement.

High frequency Data

In sample measurements, the AC magnetic moment data derived from the AC applied field does not follow the DC magnetization curve for the same sample due to interactive, dynamic effects within the sample. In high AC frequency applications, the AC magnetization of the sample lags the applied field (driving field). In measurement, the AC ‘lagging effect’ is termed an AC loss factor and is one of the more important parameters associated with AC magnetic material measurements and their applications.

AC Susceptibility measurements can be focused and localized while ‘Wide-band’ AC susceptibility measurements can also be made on samples whereby the resulting data employs an integrated reporting method for material property analysis over large frequency range. The AC material measurement can measure and report very small AC magnetic fields, and the AC property measurement can also provide material data with simultaneous AC frequency reporting.

AC Measurement Data

In AC magnetic measurements, where an AC field is applied to a sample and the resulting AC magnetic moment is measured, the resulting data is an important tool for characterizing magnetic materials. Because the induced sample’s magnetic  moment is time-dependent in the AC mode, resulting measurements yield information about magnetization dynamics which are not obtained in DC measurements.

Low to Mid-frequency Data

Low frequency measurement data is typically related to DC magnetometry results where the resulting magnetic moment of the sample follows the traditional DC magnetic, B-H curve measured with a DC magnetometer

Typical AC measurements are

  • Susceptibility vs. temperature,
  • Susceptibility vs. driving frequency,
  • Susceptibility vs. DC field offset,
  • Susceptibility vs. AC field amplitude, and frequency measurements.
  • Susceptibility vs induced magnetization in secondary coils.

Basic physical properties from the AC data are

  • Resistivity,
  • Critical temperatures,
  • Critical current density,
  • Frequency response

Susceptibility is used to characterize magnetic materials such as ferrites, Sendusts,  semiconductors, superconductors and other magnetic materials where surface barriers and effects of granularity are of performance interest. The importance of correlating the AC susceptibility data with the materials’ intrinsic structure, is of interest for many applications, when AC magnetic data is combined with ARkival’s Atomic Force Microscopy (AFM) measurements.

 

Eddy Current measurements are also possible with reference standard(s)

Remote AC Magnetic Field Applications

Application Measurements include Field data and corresponding frequency measurements for inductive coils, transformer coils and windings, flat coils, vapor deposited materials and Automotive device applications, remote communication and remote charging applications.

Using both manual AC testers and/or AC robotic testers ARkival can measure and report AC magnetic fields emanating  from AC sources in both in 2 dimensional and 3 dimensional designs and products. Field reports can be used to substantiate Finite Element calculations and results as well as produced graphic plane-plane reports that include individual field data and frequencies, Magnetic Energy plots and specific point -point Magnetic Energy values.

ARkival calibrates AC field data reporting with a variable Helmholtz coil array designed for AC Field data over different bandwidth specta.

Saturation Magnetization

Note magnetic parameter:  Saturation

Magnetic saturation is the state reached in a sample when increases in applied external magnetic field H cannot increase the magnetization of the material further. At saturation, the total magnetic flux density B does not increase with increases in applied external fields. Saturation is a characteristic of ferromagnetic and ferrimagnetic materials, such as iron, nickel, cobalt and their alloys.

Saturation is most clearly seen in the Hysteresis loop (above).. As the H field increases, the B field approaches a maximum value asymptotically, denoted as the saturation magnetization of the substance. 

Different materials have different saturation levels. High permeability iron alloys used in transformers reach magnetic saturation at 1.6–2.2 teslas (T), whereas ferrites saturate at 0.2–0.5 T.  Some amorphous alloys saturate at 1.2–1.3 T. Mu-metal saturates at around 0.8 T.

source: Wikipedia

Vibrating Sample Magnetometer (VSM)

vibrating-sample magnetometer (VSM) is an accurate scientific instrument used to measure magnetic properties.

A magnetic material sample is first magnetized via a uniform external magnetic field. The sample is then sinusoidally vibrated via linear actuator or a mechanical vibrator. The induced voltage from the magnetized sample is sensed in a close-proximity pickup coil whereby the induced voltage is proportional to the sample’s magnetic moment, which in turn,  is directly dependent on the strength of the applied magnetic field. Typically, the induced voltage is measured via a lock-in amplifier where the output is used to generate the hysteresis curve of a material during the sweep of the applied external magnetic field.

Remanence, Retentivity or Remanent Magnetization

Note magnetic parameter Retentivity,

Remanence , remanent magnetization, Retentivity  or residual magnetism is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed. After certain classes of magnet material are “magnetized” they have remanence. The remanence of magnetic materials provides the magnetic memory in magnetic storage devices, and in common magnets or easily magnetized materials. In cases where where Remanence is unwanted, it can be removed by applying a negative inducing field in a proocess often called degaussing.

In magnetic studies and applications, ARkivak measures and reports residual magnetization using a VSM Magnetometer.  The magnitude or strength of the material remanence is used to characterize permanent magnets; Neodymium magnets, for example, have a remanence approximately equal to 1.3 teslas

The default definition of magnetic remanence is the magnetization remaining in zero field after a large magnetic field is applied (enough to achieve saturation).

Source: Wikipedia

Hysteresis Loop Measurements

Note magnetic parameters of Coercivity, Saturation & Remanence

The Magnetic Hysteresis loop is the most important and significant data graph resulting from the testing of magnetic Materials and their properties. The Hysteresis loop is obtained using a precision magnetometer (Vibrating Sample Magnetometer[VSM]) using NIST and other standardized references and materials to assure relevancy of reported data for client samples.

Data available from the Hysteresis loop report from the sample measurements are several key magnetic properties… Coercivity, Saturation and Remanence, etc.

ARkival always provides Excel versions of the measured data for use in different types of magnetic analysis  programs.

Our data reporting system also has the capability of reporting your sample data in any standardized unit systems. The unit reporting request must be provided ARkival prior to the sample testing.

Magnetic Field Mapping

Magnetic Field Mapping

Many magnet applications use permanent magnets or electromagnets to provide a magnetic field for an attractive or repulsive interaction. Magnetic field data is required for product designs and applications where product function is based upon magnetic strength, the magnetized pole geometry, the external field shape and magnitude at the working distance(s) in the application. A magnetic field map can provide the effective magnetic field characteristics of application magnet(s).

ARkival performs field mapping measurements to determine magnetic field forces, field directions and distributions, and magnetic edge effects. Planar-probes or edge-directed Hall probes are used with a custom designed micrometer measurement mapping fixture to provide 3Dimensional micrometer and/or robotic-stepped planar field maps. The resulting field maps provide both the shape and magnitude of the magnetic field at different points and in 3 planar surfaces as well as at varying distances from the primary magnetic source.

Field Measurements & Distance mapping

Magnetic field data can be collected in 1, 2 or 3 data planes (X, Y & Z) at both the magnet center and magnet edges. The application magnets are positioned in a non-magnetic stand custom-machined for these measurements. The Hall-effect probes are mounted in a 3D micrometer
station providing accurate dimensional stepping in 3-planar directions. Hall-effect probes are periodically calibrated with 2 traceable
reference magnets throughout the measurement collection.

Torque Measurements

ARkival’s Torque Measurements are performed with a MicroSense VSM employing an ultra-low friction, air bearing suspending the sample with virtually zero friction. The resulting torque measurement reports the actual force on the sample. All pre-measurement calibrations are directly based upon a known torque sample. ARkival’s magnetic torque measurements can accommodate solid, bulk, and thin film samples with a torque measurement capability from 0.05 dyne-cm to 500 dyne-cm depending upon the sample magnetics, applied field, sample type and size.

Direct Magnetic torque measurements can, in some samples be more sensitive than SQUID magnetometry as our direct torque measurement is more precise and more sensitive than an indirect vector coil-based torque system.

Whereas torque is a measure of the sample’s magnetic or shape anisotropy, the magnetic torque measurement can detect magnetic phase transitions or quantum oscillations. Under certain conditions, the sample magnetization can also be extracted from the measured torque.

Magnetic Thermal Annealing (MTA)

ARkival’s Magnetic Thermal Annealing (MTA) process is used to enhance the performance of  magnetic materials and components. During their manufacture, preparation and processing the crystalline and magnetic  structures of these materials can assume moderate to high degrees of disorder.  The process of controlled  magnetic thermal annealing can remove these disorders and can often provide substantially improved magnetic performance of the materials and even their devices (e.g., spintronic devices).

The heating a magnetic material above its recrystallization temperature in a magnetic field and then cooling will allow atom migration within the crystal lattice such that the number of dislocation sites decreases, leading to the change in magnetic properties and at times, their ductility and hardness.

Magnetic materials such as  metals (in different shapes and forms… wires, foils and plates), powders and thin films can be thermally treated in temperatures up to 900˚C  in a uniform magnetic field (as high as 2.5 Tesla) and in an inert gas environment for MTA processing.

TEM (Transmission Electron Microscope)

Transmission electron microscopy (TEM) is a very high imaging magnification also performed with an electron microscope  to view thin material cross-sections and specimens (nanoparticles, tissue sections, molecules, etc) through which electrons can pass generating a projection image. TEM is analogous in many ways to the conventional (compound) light microscope with greater magnification and detail.

Image Magnification from an TEM can be controlled from 10 to 300,000 times. In magnetics, ARkival uses TEM micrograph images regularly to study minute structures, nanoparticles, minute structural detail and more.  See MNP images

EDAX (Energy Dispersive Analysis by X-Ray (EDX, EDS)

A typical EDX SPECTRA (elemental) result is shown in photo at left. The elemental spectral peaks are identified during the x-ray scan. The individual elements are indicated in the spectra by both their intensity and scan position. The greater the intensity, the higher the element concentration in the sample.

The spectra shown illustrates the elemental results for a sample containing significant amounts of Iron (Fe) and Cobalt (Co). Although these primary magnetic elements are present in the sample their weight percents vary in concentration.

The super-positioning of the comparative spectra can also be demonstrated and are summarized in the clients’ analysis reports.

The elemental weight percents for each samples is also collected. Data from these test results are used in elemental concentration Tables to identify and illustrate material composition differences. Similarities and differences are best identified by the weight percentage data from the sample data reports. The comparative elemental analysis of the different samples is also included in the Summary section of the customer report.

SEM (Scanning Electron Microscope)

Scanning electron microscopy (SEM) is a very high imaging magnification performed with an electron microscope that produces informative images of magnetic samples by scanning them with a focused beam of electrons. The electrons interact with atoms in the sample, producing highly magnified images of the sample’s surface topography and composition.

Image Magnification from an SEM can be controlled from 10 to 300,000 times. In magnetics, ARkival uses SEM micrograph images regularly to study minute structures, nanoparticles, minute structural detail, surface areas of materials, biological specimens and more.

MFM (Magnetic Force Microscopy)

MFM is a magnetic measurement technology for imaging various magnetic structures including magnetic domains, domain walls (Bloch and Neel), recorded magnetic bits and magnetic surface structures and abnormalities. MFM studies are performed with and/or without the presence of an external magnetic field.

MFM imaging of various materials such as thin films, nanoparticles, nanowires, permalloy disks and recording media are commonly performed. The technology does not require the sample to be electrically conductive and measurements are performed at ambient temperature, in ultra-high vacuum (UHV), or in a liquid environment, at different temperatures, and in the presence of external magnetic fields.

The Measurement is nondestructive to the crystal lattice or structure and is typically insensitive to minor surface contamination. No special surface preparation or coating is required.

Sample are usually scanned twice. The first scan of the surface presents the topography of the sample. In secondary scans, the magnetic tip-sample distance is increased and when scanned along the initial topography line and is only affected by the magnetic forces. The signals are electronically configured to obtain the MFM image.

This form of cantilever magnetometry (MFM) can also be used for characterizing magnetic samples and as technique to characterize the magnetic properties of materials and measure the magnetic dissipation in magnetic materials. The magnetization of individual magnetic nanoparticles (MNP) can also be determined with MFM for applications in nanomagnetism used pharma-delivery, MRI diagnostics and biotechnology.

ICP (Inductively Coupled Plasma) Analysis & Spectrometry

ICP-AES is a measurement technique that ARkival uses to determine elemental concentrations in materials from minute trace amounts to major compositions. Statistical concentration data results can be obtained for about 70 elements with detection limits in the parts per billion range.

ICP-MS is a type of mass spectrometry that ARkival uses for detecting metals and several non-metals at concentrations as low as one part in 1015 (part per quadrillion, ppq). It is used in tissue containment analysis involving exceptionally small diagnostic and treatment material quantities and types.

Environmental Testing

ARkival’s facilities house several environmental chambers for small-to-medium sized products, components and test systems. The chambers are equipped to provide acclimatization cycling with real-time temperature and humidity monitoring. The chambers are designed for flexibility and can be configured for special product requirements and testing during environmental exposure.

Geomagnetic Measurements & Air Transport Standards

ARkival Technology performs Magnetic Field testing of magnet-contained products designated for both domestic and international air shipments.  Such products are required to be magnetically source-distance-tested (and labeled ) for compliance to the required ICAO & IATA 1 specifications.

The resulting source-distance data must demonstrate magnetic fields less than the maximum value specified by ICOA & IATA documents at the seven (7’) foot and fifteen (15’) foot distances for all packaged and non-packaged products containing magnets.  ARkival’s testing process delivers actual and simulated worst-case magnetic field measurements to determine the cumulative field effect (magnetic field strength and magnetic polarity) of the magnets, magnetic products and/or magnetic materials at required planes and distances.

ARkival’s Testing includes…

Project Description for testing, evaluating and certifying shipping cartons containing Magnets and/or Magnetic devices for compliance to the ICAO guidelines for the safe transport by air.

 

Reference Documents: 

International Civil Aviation Organization (ICAO) Standards and regulations for aviation safety, security, efficiency, regularity and aviation environmental protection.

ICAO standards and other provisions: Standards and Recommended Practices (SARPs)

  •  Packing instruction: reformatted packing instructions (effective 1 January 2011) v; 6 P141 (17/10/2008) 2– and subsequent releases.
  •   Technical instructions for the safe transport of dangerous goods by air: 2011-2016 edition doc9284-an/905 add #3.crr. #2 26/4/11 and subsequent releases.
  •   IATA- Dangerous Goods Regulations- Magnetic products

 

Specific Testing

ARkival’s test procedures address this class of materials on Passenger and Cargo aircraft designated as UN 2807, Magnetized material

Measurements determine the magnetic field strength at the both distances of 2.1 m (7 ft.) and 4.6 m (15 ft.) from any point on any surface of the individually packaged units in 360 degree rotations in two planes.

For compliance, magnetic field readings resulting from tested product(s) at both specified distances and orientations should not exceed 0.159 A/m and 0.418 A/m respectively.

Measurement Equipment

All magnetic field measurements are made with Hall Effect probes with either linear or transverse sensors 3.
The laboratory test area for magnetic measurement is free from magnetic interference other than the earth’s magnetic field (~ 5 milliGauss-mG at the EW measurement (geographic) location when minimized).

The primary Hall effect Gaussmeters are all Geomagnetometers with calibrated Probe Reference Standards. Distance measurements are all
supported by a Class IIIA Laser Tape.

NOTES

1 ICAO- International Civil Aviation Organization (www.icao.int) & IATA- International Air Transport Association (www.iata.org).

http://www.iata.org/Site Collection Documents/Documents/IATA Refomatted Packing

3 The use of a highly sensitive, CMOS technology Hall probes for these measurements requires additional humidity and stray
earth field shielding during testing.

Hall Effect Measurements

ARkival has an extensive range of different types, sizes and configurations of Hall effect probes. Contact us at 603.881.3322 for more information.

ALSO See magnetic probe Discussions in sections on Magnet Magnetic Fields AND Geomagnetic Field Measurements

Dielectric Properties

ARkival offers several services to meet you Dielectric Properties measurement needs. Contact us at 603.881.3322 for more information.

Thermal Properties

ARkival offers several services to meet you Thermal Property measurement needs.  Contact us at 603.881.3322 for more information.

Magnet Field Measurements & Magnetic Field Distance Mapping

Magnetic field data from magnets or magnetized materials can be collected in 1, 2 or 3 data planes (X, Y & Z) at both the magnet center and magnet edges. The application magnets are positioned in a non-magnetic test stand custom-machined for these measurements. The Hall-effect probes are mounted in a 3D micrometer station or robotic fixture for providing accurate dimensional stepping in 3-planar directions. Hall-effect probes used are periodically calibrated with several traceable reference magnets throughout the measurement and collection.

Curie Temperature

ARkival’s Curie temperature (Tc), or Curie point measurements are designed to determine the critical temperature at which magnetic materials loose their magnetic properties. Controlled temperature tests are performed in inert gas environments to determine the temperature (or temperature range) for which magnetic losses occur and the temperature below which magnetic properties return.

Magnetic forces defined by the materials’ magnet moment result from the materials atomic structure and the determination of the Curie temperature is the point or region which a material’s intrinsic magnetic moments disorient and randomly change direction.

Our lab facilities and magnetometers enable us to apply external magnetic fields during a controlled high temperature heating process while preventing material oxidation in an inert gas environment.