physics

Nanomagnet

Nanomagnet is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Nanomagnet rather than just read about it. In short: In magnetism, a nanomagnet is a nanoscopic scale system that presents spontaneous magnetic order (magnetization) at zero applied magnetic field (remanence). The small size of nanomagnets prevents the formation of magnetic domains (see single domain (magnetic)).

Key takeaways

Nanomagnet belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Nanomagnet to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Nanomagnet from memory before moving on to harder problems.

Reference excerpt

In magnetism, a nanomagnet is a nanoscopic scale system that presents spontaneous magnetic order (magnetization) at zero applied magnetic field (remanence). The small size of nanomagnets prevents the formation of magnetic domains (see single domain (magnetic)). The magnetization dynamics of sufficiently small nanomagnets at low temperatures, typically single-molecule magnets, presents quantum phenomena, such as macroscopic spin tunnelling. At larger temperatures, the magnetization undergoes random thermal fluctuations (superparamagnetism) which present a limit for the use of nanomagnets for permanent information storage. Canonical examples of nanomagnets are grains of ferromagnetic metals (iron, cobalt, and nickel) and single-molecule magnets. The vast majority of nanomagnets feature transition metal (titanium, vanadium, chromium, manganese, iron, cobalt or nickel) or rare earth (Gadolinium, Europium, Erbium) magnetic atoms. The ultimate limit in miniaturization of nanomagnets was achieved in 2016: individual Ho atoms present remanence when deposited on an atomically thin layer of MgO coating a silver film was reported by scientists from EPFL and ETH, in Switzerland. Before that, the smallest nanomagnets reported, attending to the number of magnetic atoms, were double decker phthalocyanes molecules with only one rare-earth atom. Other systems presenting remanence are nanoengineered Fe chains, deposited on Cu2N/Cu(100) surfaces, showing either Neel or ferromagnetic ground states with in systems with as few as 5 Fe atoms with S=2. Canonical single-molecule magnets are the so-called Mn12 and Fe8 systems, with 12 and 8 transition metal atoms each and both with spin 10 (S = 10) ground states. The phenomenon of zero field magnetization requires three conditions:

A ground state with finite spin A magnetic anisotropy energy barrier Long spin relaxation time. Conditions 1 and 2, but not 3, have been demonstrated in a number of nanostructures, such as nanoparticles, nanoislands, and quantum dots with a controlled number of magnetic atoms (between 1 and 10).

References

Further reading Friedman, J. R.; Sarachik, M. P. (2010). "Single-Molecule Nanomagnets". Annual Review of Condensed Matter Physics. 1: 109–128. arXiv:1001.4194. Bibcode:2010ARCMP...1..109F. doi:10.1146/annurev-conmatphys-070909-104053. S2CID 118713965.

Worked examples

Example 1 — a first encounter with Nanomagnet

Start with the simplest possible case. Write down what Nanomagnet claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Nanomagnet before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Nanomagnet ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Nanomagnet

In research: Nanomagnet appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Nanomagnet in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Nanomagnet is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electromagnetism stubs, Magnetism, so understanding it makes those chapters shorter.
In everyday life: Look for Nanomagnet outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Nanomagnet in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Nanomagnet means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Nanomagnet out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Nanomagnet in simple terms?

Why does Nanomagnet matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Nanomagnet?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Nanomagnet.