Giant Magnetoimpedance Properties in Amorphous Magnetic Materials

Giant magnetoimpedance describes the substantial variation in the electrical impedance of a soft magnetic conductor when subjected to an external magnetic field. In amorphous magnetic materials, free from long-range crystalline order, the homogeneous distribution of internal stresses and absence of grain boundaries yield exceptional magnetic softness. Combined with frequency-dependent skin effects, these characteristics enable impedance changes of several orders of magnitude under modest fields. The interplay between internal stress, magnetic anisotropy and magnetostriction governs the field and frequency dependence of the GMI ratio. Careful control of composition and post-processing treatments such as annealing or stress-annealing can tailor the radial distribution of magnetic domains and transverse anisotropy, thereby maximising sensitivity. The remarkable field responsiveness, broad frequency bandwidth and thermal stability of GMI in amorphous wires and ribbons underpin a range of sensing technologies, from pico-Tesla magnetic field detectors to compact biosensors and structural health monitors. Global efforts continue to refine material design, optimise device geometry and integrate GMI elements with microfabrication techniques, advancing both fundamental understanding and practical applications.

Research from Nature Portfolio

Recent studies have demonstrated that stress-annealing of Fe-rich glass-coated microwires can increase the giant magnetoimpedance ratio by an order of magnitude. By varying annealing temperature and applied tensile stress, researchers have induced compressive back-stresses and modified short-range ordering, leading to a marked decrease in coercivity and the emergence of linear hysteresis loops. These adjustments to internal stress profiles and magnetic anisotropy distributions result in enhanced GMI sensitivity at high frequencies, offering a pathway to cost-effective soft magnetic materials for advanced sensing devices.

Giant Magnetoimpedance Properties in Amorphous Magnetic Materials publication trend

The graph below shows the total number of articles in giant magnetoimpedance properties in amorphous magnetic materials across all publications each year (not limited to Nature Index journals).

Technical terms

Giant Magnetoimpedance (GMI): The large change in electrical impedance of a soft magnetic conductor in response to an external magnetic field, driven by variations in skin depth and magnetic permeability.

Amorphous Magnetic Material: A magnetic alloy lacking long-range crystalline order, offering uniform internal stresses and high magnetic softness.

Magnetic Anisotropy: The directional dependence of a material’s magnetic properties, which can be engineered through composition, stress or heat treatment.

Stress-Annealing: A post-processing technique in which a material is heated under applied mechanical stress to modify internal stress distributions and induce preferred magnetic anisotropies.

References

1. Exploring the temperature dependence of magnetic properties and magnetoimpedance effect in Co-rich microwires. Journal of Science Advanced Materials and Devices (2024).
2. Tailoring of magnetoimpedance effect and magnetic softness of Fe-rich glass-coated microwires by stress- annealing. Scientific Reports (2018).
3. Optimization of magnetic properties and GMI effect of Thin Co-rich Microwires for GMI Microsensors. Sensors (2020).
4. Design and Fabrication of a Miniaturized GMI Magnetic Sensor Based on Amorphous Wire by MEMS Technology. Sensors (2018).
5. Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review. Sensors (2015).