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The Curie point (Tc), or Curie temperature, is a term in physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
 and materials science
Materials science

Materials science or materials engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering....
, named after Pierre Curie
Pierre Curie

Pierre Curie was a French Physics, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate. In 1903 he received the Nobel Prize in Physics with his wife, Marie Curie, and Henri Becquerel, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phe...
 (1859-1906), and refers to a characteristic property of a ferromagnetic or piezoelectric material.

Curie point of a ferromagnetic material is the temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 above which it loses its characteristic ferromagnetic
Ferromagnetism

Ferromagnetism is the basic mechanism by which certain materials form permanent magnets and/or exhibit strong interactions with magnets; it is responsible for most phenomena of magnetism Magnet#Common uses of magnets ....
 ability (768°C or 1414 °F for iron).






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The Curie point (Tc), or Curie temperature, is a term in physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
 and materials science
Materials science

Materials science or materials engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering....
, named after Pierre Curie
Pierre Curie

Pierre Curie was a French Physics, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate. In 1903 he received the Nobel Prize in Physics with his wife, Marie Curie, and Henri Becquerel, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phe...
 (1859-1906), and refers to a characteristic property of a ferromagnetic or piezoelectric material.

Curie point in ferromagnetic materials

The Curie point of a ferromagnetic material is the temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 above which it loses its characteristic ferromagnetic
Ferromagnetism

Ferromagnetism is the basic mechanism by which certain materials form permanent magnets and/or exhibit strong interactions with magnets; it is responsible for most phenomena of magnetism Magnet#Common uses of magnets ....
 ability (768°C or 1414 °F for iron). At temperatures below the Curie point the magnetic moment
Magnetic moment

In physics, astronomy, chemistry, and electrical engineering, the term magnetic moment of a system usually refers to its magnetic dipole moment, and is a measure of the strength of the system's net Magnetism....
s are partially aligned within magnetic domains in ferromagnetic materials. As the temperature is increased towards the Curie point, the alignment (magnetization) within each domain decreases. Above the Curie point, the material is purely paramagnetic
Paramagnetism

Paramagnetism is a form of magnetism which occurs only in the presence of an externally applied magnetic field. Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than 1 ....
 and there are no magnetized domains of aligned moments.

At temperatures above the Curie point, an applied magnetic field has a paramagnetic effect on the magnetization, but the combination of paramagnetism with ferromagnetism leads to the magnetization following a hysteresis
Hysteresis

A system with hysteresis can be summarized as a system that may be in any number of states, independent of the inputs to the system. To be exact, a system with hysteresis exhibits path-dependence, or "rate-independent memory"....
 curve with the applied field strength. The destruction of magnetization at the Curie temperature is a second-order phase transition
Phase transition

In thermodynamics, a phase transition is the transformation of a thermodynamic system from one phase to another.At phase-transition point, physical properties may undergo abrupt change- for instance, volume of the two phases may be vastly different....
 and a critical point
Critical point (thermodynamics)

In physical chemistry, thermodynamics, chemistry and condensed matter physics, a critical point, also called a critical state, specifies the conditions at which a phase boundary ceases to exist....
 where the magnetic susceptibility
Magnetic susceptibility

In electromagnetism the magnetic susceptibility is the degree of magnetization of a material in response to an applied magnetic field....
 is theoretically infinite.

One application of this effect is in magneto-optical storage media, where it is used for erasing and writing of new data. Famous examples include the Sony
Sony

is a multinational corporation list of conglomerates corporation headquartered in Minato, Tokyo, Japan, and one of the world's largest media conglomerates with revenue exceeding US$99.1 billion ....
 Minidisc
MiniDisc

A MiniDisc is a magneto-optical disc-based data storage device initially intended for storage of up to 80 minutes of digitized sound. Today, in the form of Hi-MD, it has developed into a general-purpose storage medium in addition to greatly expanding its audio roots....
 format, as well as the defunct CD-MO
CD-RW

Compact Disc ReWritable is a rewritable optical disc format. Known as CD-Erasable during its development, CD-RW was introduced in 1997, and was preceded by the never officially released CD-RW#CD-MO in 1988....
 format.

Other uses include temperature control in soldering iron
Soldering iron

A soldering iron is a "device" for applying heat to melt solder for attaching two metal parts.A soldering iron is composed of a heated metal tip and an insulated handle....
s such as the Weller WTCPT and, in general, where a temperature-controlled magnetization is desirable.

Curie temperature in piezoelectric materials

In analogy to ferromagnetic materials, the Curie temperature is also used in piezoelectric materials to describe the temperature above which the material loses its spontaneous polarization and piezoelectric characteristics. In lead zirconate titanate
Lead zirconate titanate

Lead zirconate titanate is a ceramic perovskite material that shows a marked piezoelectricity.It is also known as PZT which is an abbreviation of the chemical formula....
 (PZT), the material is tetragonal below Tc and the unit cell contains a displaced central cation and hence a net dipole moment
Dipole moment

Dipole moment refers to the quality of a system to behave like a dipole. Dipole moment is the measured polarity of a polar covalent bond. It is defined as the product magnitude of charge on the atoms and the distance between the two bonded atoms....
. Above Tc, the material is cubic and the central cation is no longer displaced from the centre of the unit cell. Hence, there is no net dipole moment and no spontaneous polarization.

Curie-Weiss law

See also

  • See ferromagnetism
    Ferromagnetism

    Ferromagnetism is the basic mechanism by which certain materials form permanent magnets and/or exhibit strong interactions with magnets; it is responsible for most phenomena of magnetism Magnet#Common uses of magnets ....
     for a list of ferromagnetic materials and their Curie temperatures.
  • Ferroelectric effect
  • Néel temperature
    Néel temperature

    The N?el temperature, TN, is the temperature at which an antiferromagnetic material becomes paramagnetic — that is, the thermal energy becomes large enough to destroy the macroscopic magnetic ordering within the material....
  • Pierre Curie
    Pierre Curie

    Pierre Curie was a French Physics, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate. In 1903 he received the Nobel Prize in Physics with his wife, Marie Curie, and Henri Becquerel, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phe...


External links

  • . Video by Walter Lewin
    Walter Lewin

    Walter H. G. Lewin is currently a professor of physics at the Massachusetts Institute of Technology ....
    , M.I.T.