Pierre Curie (1859 - 1906), was an French physicist and physical chemist and co-winner of the Nobel Prize for Physics in 1903, one of the founders of the physics of magnetism.

He and his wife, Marie Curie, discovered radium and polonium in their investigation of radioactivity.
Pierre Curie was educated by his father, a doctor. Curie developed a passion for mathematics at the age of 14 and showed a particular aptitude for spatial geometry, which was later to help him in his work on crystallography. Matriculating at the age of 16 and obtaining his licence es sciences at 18, he was in 1878 taken on as laboratory assistant at the Sorbonne. There Curie carried out his first work on the calculation of the wavelength of heat waves.
This was followed by very important studies on crystals, in which he was helped by his elder brother Jacques. The problem of the distribution of crystalline matter according to the laws of symmetry was to become one of his major preoccupations. The Curie brothers associated the phenomenon of pyroelectricity with a change in the volume of the crystal in which it appears, and thus they arrived at the discovery of piezoelectricity. Later, Pierre was able to formulate the PRINCIPLES OF SYMMETRY, which states the impossibility of bringing about a specific physical process in an environment lacking a certain minimal dissymmetry characteristic of the process. Further, this dissymmetry cannot be found in the effect if it is not preexistent in the cause. He went on to define the symmetry of different physical phenomena.

Pierre Curie contributed much to our understanding of the role of symmetry and asymmetry in physical phenomena. It were Pierre Curie and his brother Jacques who discovered piezoelectricity, i.e., how a crystal, of sufficiently low symmetry develops an electric polarization under the influence of an external mechanical force.
Pierre Curie also carried out profound theoretical researches. His excellent crystallographic education led him to understand very early the importance of symmetry considerations. All this led him to global considerations on symmetry in physical phenomena, described in his 1894 paper.
Curie described the properties associated with the symmetry of fields (vectors, pseudovectors, scalars, pseudoscalars. etc.). On the other hand, he announced an essential principle relating the symmetry of "effects" to the symmetry of "causes." That which we mean here by "cause" and "effect" is not derived from grand philosophical arguments but rather from concrete examples.
A detailed analysis of the works of Pierre Curie with especial attention to the role of symmetry were carried out in the papers:
P. G. De Gennes,
Pierre Curie and the role of symmetry in physical laws.
Ferroelectrics, v.40, No 1, 125-129 (1982).
A. L. Kuzemsky,
Statistical mechanics and the physics of many-particle model systems.
Physics of Particles and Nuclei, {\bf 40}, 949 (2009).

Appointed supervisor (1882) at the School of Physics and Industrial Chemistry at Paris, Curie resumed his own research and, after a long study of buffered movements, managed to perfect the analytical balance by creating an aperiodic balance with direct reading of the last weights. Then he began his celebrated studies on magnetism. He undertook to write a doctoral thesis with the aim of discovering if there exist any transitions between the three types of magnetism: ferromagnetism, paramagnetism, and diamagnetism. In order to measure the magnetic coefficients, he constructed a torsion balance that measured 0.01 mg, which, in a simplified version, is still used and called the magnetic balance of Curie and Cheneveau. He discovered that the magnetic coefficients of attraction of paramagnetic bodies vary in inverse proportion to the absolute temperature--Curie's Law. He then established an analogy between paramagnetic bodies and perfect gases and, as a result of this, between ferromagnetic bodies and condensed fluids. The totally different character of paramagnetism and diamagnetism demonstrated by Curie was later explained theoretically by Paul Langevin. In 1895 Curie defended his thesis on magnetism and obtained a doctorate of science.

The Curie-Weiss law describes the magnetic susceptibility of a ferromagnet in the paramagnetic region above the Curie point:

,

where

is the magnetic susceptibility

C is a material-specific Curie constant

T is absolute temperature, measured in kelvins

T_c is the Curie temperature, measured in kelvins

The susceptibility has a singularity at T = T_c. At this temperature and below there exists a spontaneous magnetization.

In many materials the Curie-Weiss law fails to describe the susceptibility in the immediate vicinity of the Curie point, since it is based on a mean-field approximation. Instead, there is a critical behavior of the form

with the critical exponent . However, at temperatures the expression of the Curie-Weiss law still holds, but with representing a temperature which is somewhat higher than the actual Curie temperature.

In the spring of 1894 Curie met Marie Sklodowska. Ttheir marriage (July 25, 1895) marked the beginning of a world-famous scientific achievement, beginning with the discovery (1898) of polonium and then of radium. The phenomenon of radioactivity, discovered (1896) by Henri Becquerel, had attracted Marie Curie's attention, and she and Pierre determined to study a mineral, pitchblende, the specific activity of which is superior to that of pure uranium. While working with Marie to extract pure substances from ores, an undertaking that really required industrial resources but that they achieved in relatively primitive conditions, Pierre himself concentrated on the physical study (including luminous and chemical effects) of the new radiations. Through the action of magnetic fields on the rays given out by the radium, he proved the existence of particles electrically positive, negative, and neutral; these Ernest Rutherford was afterward to call alpha, beta, and gamma rays. Pierre then studied these radiations by calorimetry and also observed the physiological effects of radium, thus opening the way to radium therapy.\\ Refusing a chair at the University of Geneva in order to continue his joint work with Marie, Pierre Curie was appointed lecturer (1900) and professor (1904) at the Sorbonne. He was elected to the Academy of Sciences (1905), having in 1903 jointly with Marie received the Royal Society's Davy Medal and jointly with her and Becquerel the Nobel Prize for Physics. He was run over by a dray in the rue Dauphine in Paris in 1906 and died instantly. An exceptional physicist, he was one of the main founders of modern physics. His complete works were published in 1908:
P. Curie, Oeuvres publiees par les soins de la Societe Francaise de Physique. (Gauthier-Villars, Paris, 1908).