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Most students know Pierre Curie as Marie Curie's husband and fellow Nobel laureate. Before radium, though, he made two discoveries that sit inside quartz watches, ultrasound machines and your Class 12 magnetism chapter. This post covers what he found, works through the numbers, and shows how to use the ideas in exams.
Who was Pierre Curie?
According to his Nobel Prize facts page, Pierre Curie was born in Paris on 15 May 1859 and died there on 19 April 1906. He shared the 1903 Nobel Prize in Physics with Henri Becquerel and Marie Curie, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel."
His Nobel biography says he was taught at home before entering the Faculty of Sciences at the Sorbonne. He became a demonstrator in physics, was put in charge of practical work at the Paris School of Industrial Physics and Chemistry in 1882, and obtained his doctorate in 1895. He was killed in a street accident in Paris. Read our post on Marie Curie's two Nobel Prizes for the radium story.
What is piezoelectricity?
In 1880 Pierre and his older brother Jacques reported their discovery in the Bulletin de la Société minéralogique de France. They studied crystals whose two ends along an axis are not symmetric. Such crystals were already known to become charged when heated. The brothers showed that pressure does something similar: compress the crystal along that axis and opposite charges appear at its two ends. The charge appears only while the pressure is changing. Release the pressure and the signs reverse.
The name comes from the Greek for "push". HyperPhysics at Georgia State University notes that quartz shows the effect and is very stable, which is why quartz crystals keep time in watches, and that piezoelectric ceramics are used in ultrasonic transducers for medical imaging. The effect works both ways: a voltage makes the crystal change shape slightly.
What is the Curie temperature?
The Nobel biography says Curie "showed that the magnetic properties of a given substance change at a certain temperature – this temperature is now known as the Curie point." Above it, a ferromagnet such as iron loses its strong magnetism. HyperPhysics on ferromagnetism explains that the property disappears as a result of thermal agitation, and its table of Curie temperatures gives 1043 K for iron, 1388 K for cobalt, 627 K for nickel and 293 K for gadolinium.
Paramagnetic materials follow Curie's law: their magnetisation in a given field is inversely proportional to the absolute temperature.
Worked example: Curie temperatures and Curie's law
Convert to Celsius. Iron: 1043 − 273.15 = 769.85 °C, about 770 °C. Nickel: 627 − 273.15 = 353.85 °C, about 354 °C. Gadolinium: 293 − 273.15 = 19.85 °C, about 20 °C. So gadolinium is ferromagnetic in a cold room and loses that property on a warm day.
Use Curie's law. A paramagnetic sample has susceptibility χ at 300 K. What is it at 150 K and at 600 K? Since χ ∝ 1/T, χ(150 K) = χ × 300/150 = 2χ, and χ(600 K) = χ × 300/600 = χ/2.
The common mistake is to use Celsius in step 2. Curie's law needs absolute temperature, just like the gas laws.
Where does this appear in your syllabus?
The NCERT Class 12 chapter Magnetism and Matter describes dia-, para- and ferromagnetism and the effect of temperature on them. The JEE (Main) 2026 syllabus lists "para-, dia- and ferromagnetic substances with examples, the effect of temperature on magnetic properties". Piezoelectricity itself is not in the JEE Main syllabus, but it makes a strong example in projects and interviews. Check the current syllabus for your exam. For more on magnetic materials, see our post on hysteresis and magnetic materials.
What can a student take from Pierre Curie's way of working?
Look for symmetry. The brothers searched for the effect in crystals whose shape lacks symmetry, the same crystals already known to charge up when heated.
Build your own instruments. His Nobel biography lists balances, electrometers and piezoelectric crystals he constructed for his experiments.
Work with others. Piezoelectricity came from work with his brother, and radioactivity from work with his wife.
If domains and susceptibility are hard to picture, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read.
Try it now: a paramagnetic salt has χ = 3.0 × 10⁻⁴ at 27 °C. Use Curie's law to find χ at −73 °C.
