White Paper: High-temperature FORC study of single- and multi-phase permanent magnets
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High-temperature FORC study of singleand multi-phase permanent magnets
The FORC diagram is a 2D or 3D contour plot of ρ(Ha, Hb). It is common to change the coordinates from (Ha, Hb) to Hc = (Hb – Ha)/2 and Hu = (Hb + Ha)/2, where Hu represents the distribution of interaction or reversal fields, and Hc represents the distribution of switching or coercive fields.
LAKE SHORE CRYOTRONICS, INC. WHITE PAPER
High-temperature FORC results for multi-phase permanent magnets
Brad C. Dodrill, Jeffrey R. Lindemuth, Cosmin Radu, and Harry S. Reichard
F
irst-order-reversal-curves (FORCs) are a nondestructive tool for characterizing the magnetic properties of materials comprised of fine (micron- or nanoscale) magnetic particles. FORC measurements and analysis have long been the standard protocol used by geophysicists and earth and planetary scientists investigating the magnetic properties of rocks, soils, and sediments. A FORC can distinguish between single-domain, multi-domain, and pseudo single-domain behavior, and it can distinguish between different magnetic mineral species.1 More recently, FORC has been applied to a wider array of magnetic material systems, because it yields information regarding magnetic interactions and coercivity distributions that cannot be obtained from measurements of a material’s major hysteresis loop alone. In this article, we discuss the FORC measurement and analysis technique and present high-temperature FORC results for multi-phase permanent magnets.
Magnetization measurements and first-order-reversal-curves The most common measurement that is performed to characterize a material’s magnetic properties is measurement of the major hysteresis loop M(H) using either a vibrating sample magnetometer or superconducting quantum interference device magnetometer. The parameters that are most commonly extracted
Brad C. Dodrill, Lake Shore Cryotronics Jeffrey R. Lindemuth, Lake Shore Cryotronics Cosmin Radu, Lake Shore Cryotronics Harry S. Reichard, Princeton Measurement Corp. (Lake Shore Cryotronics) The MRS Corporate Partner Program supports the Materials Research Society Foundation.
To demonstrate the utility of the FORC measurement and analysis protocol for magnetic property measurements, the characterization of high-temperature magnetic properties of materials is presented. Measurements were conducted for a synthetically produced three-phase magnet by mixing together, in approximate equal mass proportions, three different single-phase magnets: Sr-ferrite powder (Hoosier Magnetics), BaSr ceramic (Magnet Sales & Manufacturing – Integrated Magnetics), and sintered NdFeB (Magnequench). All magnetic measurements were performed using a Lake Shore Cryotronics MicroMag vibrating sample magnetometer with a hightemperature furnace, which allows for variable temperature measurements from room temperature to 800°C. All measured magnetization data are presented in terms of the magnetic moment (emu) as a function of field (Oe) and temperature (°C). There are a number of open source FORC a
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