science

Low field magnetoresistance

Low field magnetoresistance is a science 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 Low field magnetoresistance rather than just read about it. In short: Low field magnetoresistance' ("LFMR") is the tendency of some materials, such as perovskite crystals, to increase their electrical resistance, when under the effect of a low strength magnetic field. LFMR is a form of magnetoresistance.

Key takeaways

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

Reference excerpt

Low field magnetoresistance' ("LFMR") is the tendency of some materials, such as perovskite crystals, to increase their electrical resistance, when under the effect of a low strength magnetic field. LFMR is a form of magnetoresistance. This is caused by spin polarised tunneling, and spin dependent scattering, across large angle boundaries.

Discovery from CMR research Colossal magnetoresistance (CMR) was a known property in many perovskite oxides. However, this required a large external magnetic field, which hindered the practical applications, as a colossal magnetic field could not be generated outside of the lab. This led to two approaches to finding a more practical form of magnetoresistance.

Looking to find the original cause of CMR from the theoretical side Finding ways to improve the strength of the CMR effect Large, as opposed to colossal, magnetoresistance had already been reported in doped LaMnO3 polycrystal samples, at relatively low magnetic fields. This was in contrast to single crystal samples which required larger magnetic fields. This led to the discovery that spin polarized tunneling and spin dependent scattering across large angle boundaries lead to Low field magnetoresistance (LFMR).

LFMR in Epitaxial Films In order to obtain LFMR in epitaxial thin films (single-crystal like materials), epitaxial strain has been used. Wang and Li reported an enhancement of the magnetoresistance in 5- to 15-nm-thick Pr0.67Sr0.33MO3 films using out-of-plane tensile strain. In a conventional strain engineering framework, epitaxial strain is only effective below the critical thickness, which is usually less than a few tens of nanometers. Tuning electron transport by epitaxial strain has only been achieved in ultrathin layers because of the relaxation of epitaxial strains in relatively thick films. Vertically aligned heteroepitaxial nanoscaffolding films have been proposed to generate strain in thick films. A vertical lattice strain as large as 2% has been achieved in La0.7Sr0.3MnO3:MgO vertical nanocomposites. The magnetoresistance, magnetic anisotropy, and magnetization can be tuned by the vertical strain in films over few hundred nanometers thick.

References

Worked examples

Example 1 — a first encounter with Low field magnetoresistance

Start with the simplest possible case. Write down what Low field magnetoresistance claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Low field magnetoresistance 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 Low field magnetoresistance 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 Low field magnetoresistance

In research: Low field magnetoresistance appears in science 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 Low field magnetoresistance 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: Low field magnetoresistance is common in secondary-school and first-year university syllabi. It links to neighbouring topics Thin films, so understanding it makes those chapters shorter.
In everyday life: Look for Low field magnetoresistance 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 Low field magnetoresistance in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Low field magnetoresistance 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 Low field magnetoresistance out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Low field magnetoresistance in simple terms?

Why does Low field magnetoresistance matter?

Because it connects several science 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 Low field magnetoresistance?

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 Low field magnetoresistance.