What Is Magnetic Analysis?

Magnetic analysis is the characterization of materials and systems through the measurement and interpretation of their magnetic properties. It encompasses the experimental techniques used to quantify magnetization, susceptibility, coercivity, and energy loss, as well as the computational methods that model these quantities from first principles or empirical relations. The discipline is central to materials science, power engineering, and data storage technology, where the magnetic behavior of a material determines its suitability for motors, transformers, sensors, and recording media.

Magnetic analysis is conducted across multiple length scales. At the atomic level, it examines how spin and orbital contributions to the magnetic moment of individual atoms combine to produce bulk magnetism. At the microstructural level, it traces how domain structure and grain boundaries govern the response of a material to an applied field. At the device level, it measures the integrated losses and flux distributions that determine the efficiency of a transformer core or the switching energy of a magnetic memory element.

Magnetization and Hysteresis

Magnetization describes the density of magnetic dipole moments in a material per unit volume. When an external field is applied, the magnetization of a ferromagnetic material increases as magnetic domains whose moments are aligned with the field grow at the expense of unfavorably oriented domains. The relationship between applied field (H) and resulting flux density (B) is captured by the hysteresis loop, a closed curve traced when H is cycled through positive and negative saturation.

Key parameters extracted from the hysteresis loop include saturation magnetization (the maximum achievable moment), remanence (the residual magnetization at zero applied field), and coercivity (the field required to reduce magnetization to zero). AIP Advances research on hysteresis characteristics in ferromagnetic materials demonstrates how these parameters vary with DC bias, frequency, and temperature, findings that directly inform transformer and motor core design.

The area enclosed by the hysteresis loop is proportional to the energy dissipated per cycle as heat. Minimizing this loss is the primary objective in soft magnetic material selection for power applications. MDPI's study on magnetic hysteresis loop measurement systems describes modern fluxmeter-based instruments capable of resolving B-H loops on 3D-printed composite cores, extending measurement capability to novel additive-manufactured magnetic components.

Magnetic Susceptibility

Magnetic susceptibility is the ratio of the induced magnetization to the applied field in the linear response regime, quantifying how readily a material becomes magnetized. Paramagnetic materials have small positive susceptibilities; ferromagnetic materials have large positive susceptibilities that are field-dependent and temperature-sensitive; diamagnetic materials have small negative values and are repelled rather than attracted by fields.

A tutorial in Communications Physics on interpreting magnetic susceptibility data with the Curie-Weiss law explains how the temperature dependence of susceptibility reveals the nature of magnetic ordering in a material and provides estimates of exchange coupling constants, information used in materials discovery and in characterizing newly synthesized compounds.

Flux Measurements and Characterization Methods

Flux measurements determine the total magnetic flux passing through a cross-section of a core or air gap, which is the integrated B field over the area. Fluxmeters, search coils, and Hall-effect probes are standard instruments. In AC measurements, lock-in amplifiers extract the in-phase and quadrature components of flux, separating loss and storage contributions.

Complementary characterization methods include vibrating sample magnetometry (VSM), superconducting quantum interference device (SQUID) magnetometry for low-moment samples, and magnetic force microscopy (MFM) for spatially resolved domain imaging. Each technique targets a different combination of sensitivity, spatial resolution, and operating field range.

Applications

Magnetic analysis supports engineering and research across a range of technical domains:

• Power electronics: Core loss characterization for transformer and inductor materials at operating frequency and temperature
• Electric motors: Measurement of rotor and stator lamination properties to predict efficiency and thermal performance
• Data storage: Hysteresis loop analysis to qualify media for magnetic hard disk drives and tape systems
• Magnetic sensors: Susceptibility and permeability measurements for magnetoresistive and fluxgate sensor development
• Materials discovery: Screening of new alloys and composites for permanent magnet applications in motors and generators
• Biomedical imaging: Characterization of superparamagnetic nanoparticles used as MRI contrast agents