What is Nanomagnetics?

To put this into perspective, a nanometre is one-billionth of a metre, making these structures incredibly small.

This field intersects with other advanced areas such as nanotechnology, the study of materials at the atomic or molecular scale, material science, which examines the properties of matter, and condensed matter physics, which looks at the physical properties of solid and liquid matter. Nanomagnetics offers numerous applications, ranging from how we store data to innovative medical treatments.

Fundamental principles

When materials are shrunk down to the nanoscale, their magnetic properties can change drastically compared to their larger, bulk counterparts. This is because at such small scales, the surface area relative to the volume increases, making surface effects (the influences at the material's outer layer), quantum effects (the strange behaviours that occur at atomic and subatomic levels), and interactions between different magnetic regions within the material more significant.

Some of the key concepts in nanomagnetics include:

• Superparamagnetism occurs in tiny particles where the direction of magnetisation can flip randomly due to thermal energy. Unlike larger ferromagnetic materials, which retain their magnetisation without an external magnetic field, these nanoparticles do not hold onto their magnetisation when the field is removed.
• Exchange bias is a phenomenon seen in nanoscale materials where an antiferromagnetic material (one in which the magnetic moments of atoms or ions cancel each other out) is paired with a ferromagnetic one (where magnetic moments align), causing a shift in the magnetic response of the ferromagnet.
• Spintronics is a cutting-edge technology that leverages not only the charge of electrons (as in traditional electronics) but also their spin (a quantum property that gives particles their magnetic moment) for processing information. Nanoscale magnetic materials are essential for developing these advanced spintronic devices.

Applications

Nanomagnetics has found a wide range of applications across various industries. For instance, in the field of data storage, conventional magnetic storage devices like hard drives are nearing their capacity limits. Nanomagnetic materials, however, have the potential to store data at much higher densities, paving the way for the next generation of memory devices, such as Magnetoresistive Random Access Memory (MRAM).

In medicine, magnetic nanoparticles are being utilised for targeted drug delivery, where the particles are directed to specific areas in the body, or in enhancing the contrast of Magnetic Resonance Imaging (MRI) scans, which helps in better diagnosis. Moreover, these nanoparticles can be employed in hyperthermia treatments for cancer, where they are heated by an external magnetic field to destroy cancer cells.

Nanomagnetic sensors are another critical application. Due to their high sensitivity and compact size, these sensors are used in various fields, including detecting tiny changes in magnetic fields, which is particularly useful in automotive applications, industrial automation, and consumer electronics.

Furthermore, nanomagnetic structures are being explored in quantum computing as potential qubits, the fundamental units of quantum information. These structures are promising because they can maintain their quantum state (coherence) for longer periods, which is crucial for the development of practical quantum computers.

Challenges and future prospects

While the potential of nanomagnetic materials and devices is vast, there are significant challenges in developing them. Fabricating materials at such small scales is complex, and understanding and controlling the quantum effects that become dominant at these sizes adds another layer of difficulty. Additionally, ensuring that these materials remain stable and reliable in real-world applications is a critical challenge that researchers are continuously working to overcome.

Despite these hurdles, the field of nanomagnetics is advancing rapidly, driven by the growing need for smaller, faster, and more energy-efficient devices. As research progresses, nanomagnetics is expected to play an increasingly important role in a wide range of advanced technologies​.