Magnetics Business & Technology - Summer 2017 - 9

FEATURE ARTICLE
point in only 69 seconds.
As noted previously, the first-order-reversal-curve (FORC) technique is becoming
increasingly important in characterizing magnetic material properties because it provides information regarding magnetic interactions and coercivity distributions, information that cannot be obtained from a hysteresis loop measurement alone. A typical
series of FORCs can contain thousands of data points and thus the measurement can
be very time consuming if the measurement speed of the magnetometer is slow.
Figure 4 shows 46 FORCs (2,012 data points) recorded at 30 ms/point in 4 minutes 32
seconds for the same magnetic stripe sample shown in figure 3 (top), and 100 FORCs
(8,818 data points) recorded at 500 ms/point in 1 hour and 20 minutes for the same
CoPt thin film shown in figure 3 (bottom).

Summary

In this article we have discussed the advantages and disadvantages of the most
commonly used inductive and force based magnetometry methods. We've presented
measured RMS noise data for an electromagnet based VSM[12] as function of signal averaging, and also typical results for a CoPt thin film with saturation moment of only 20
µemu. Results of fast hysteresis loop and FORC measurements have been presented
as well demonstrating the measurement speed of the VSM, which is particularly important in acquiring FORC data.

Figure 3. A 13 second hysteresis loop at 10 ms/
point for a 14 memu magnetic stripe (top) and 69
second hysteresis loop at 100 ms/point for a 80
μemu CoPt thin film (bottom).

Brad C. Dodrill graduated from The Ohio State University in 1982 with a BSc degree
in Physics and a minor in Mathematics. He completed 2 years of graduate studies in
Physics and Electrical Engineering and took a position with Lake Shore Cryotronics in
1984 as a Research Scientist. He is currently the Vice President of Sales and a Senior
Scientist at Lake Shore. In his technical capacity, he is active in applications and product development initiatives in the areas of magnetic and electronic measurements and
materials. He has 40 paper publications to his credit, holds three US patents, and has
lectured at numerous universities and technical conferences in the US, Europe and Asia.
For more information, visit lakeshore.com.
References

Figure 4. A 4 minute 32 second measurement of 46
FORCs for a 14 memu magnetic stripe (top) and a
1 hour and 20 minute measurement of 100 FORCs
for a 80 µemu CoPt thin film (bottom).

www.MagneticsMagazine.com

[1] C. R. Pike, A. P. Roberts, K. L. Verosub, "Characterizing Interactions in Fine Particle Systems
Using First-Order-Reversal-Curves", J. Appl. Phys., 85, 6660, 1999.
[2] A. P. Roberts, C. R. Pike, K. L. Verosub, "First-Order Reversal-Curve Diagrams: A New Tool
for Characterizing the Magnetic Properties of Natural Samples", J. Geophys. Res., 105, 461, 2000.
[3] B. F. Valcu, D. A. Gilbert, K. Liu, "Fingerprinting Inhomogeneities in Recording Media Using
the First Order Reversal Curve Method", IEEE Trans. Mag., 47, 2988, 2011.
[4] M. Winklhofer, R. K. Dumas, K. Liu, "Identifying Reversible and Irreversible Magnetization
Changes in Prototype Patterned Media Using First- and Second-Order Reversal Curves", J.
Appl. Phys, 103, 07C518, 2008.
[5] B. C. Dodrill, L. Spinu, "First Order Reversal Curve Analysis of Nanoscale Magnetic
Materials", Technical Proceedings of the 2014 NSTI Nanotechnology Conference and Expo,
CRC Press, 2014.
[6] Y. Cao, M. Ahmadzadeh, K. Xe, B. Dodrill, J. McCloy, "Simulation and Quantitative Analysis
of FORC Diagrams for Single Phase and Multiphase System Using Preisach Hysteron
Distribution Pattern", submitted to J. Mag. Mag. Mat., 2017.
[7] B. C. Dodrill, "First Order Reversal Curve (FORC) Studies of Nanoscale Magnetic Materials",
Technical Proceedings of the 2017 TechConnect World Innovation Conference and Expo,
CRC Press, 2017
[8] B. C. Dodrill, "First-Order-Reversal-Curve Analysis of Nanocomposite Permanent Magnets",
Technical Proceedings of the 2015 TechConnect World Innovation Conference and Expo,
CRC Press, 2015.
[9] B. C. Dodrill, "First-Order-Reversal-Curve Analysis of Multi-phase Ferrite Magnets",
Magnetics Business and Technology, Spring 2015.
[10] C. Carvallo, A. R. Muxworthy, D. J. Dunlop, "First-Order-Reversal-Curve (FORC) Diagrams
of Magnetic Mixtures: Micromagnetic Models and Measurements", Physics of the Earth
and Planetary Interiors, 154, 308, 2006.
[11] S. Foner, "Versatile and Sensitive Vibrating Sample Magnetometer", Rev. Sci. Inst., 30, 548, 1959.
[12] Lake Shore Cryotronics, USA; www.lakeshore.com
[13] Microsense, USA; www.microsense.net
[14] Quantum Design, USA; www.qdusa.com
[15] Cryogenic Limited, UK; www.cryogenic.co.uk

Summer 2017 * Magnetics Business & Technology

http://www.lakeshore.com http://www.lakeshore.com http://www.microsense.net http://www.qdusa.com http://www.cryogenic.co.uk http://www.MagneticsMagazine.com

Table of Contents for the Digital Edition of Magnetics Business & Technology - Summer 2017