What is "curie temperature"

n. (context chemistry physics English) The temperature at which the magnetism of a substance changes, specifically when a ferromagnetic material becomes paramagnetic.

In physics and materials science, the Curie temperature , or Curie point, is the temperature at which certain materials lose their permanent magnetic properties, to be replaced by induced magnetism. The Curie temperature is named after Pierre Curie, who showed that magnetism was lost at a critical temperature.

The force of magnetism is determined by the magnetic moment, a dipole moment within an atom which originates from the angular momentum and spin of electrons. Materials have different structures of intrinsic magnetic moments that depend on temperature; the Curie temperature is the critical point at which a material's intrinsic magnetic moments change direction.

Permanent magnetism is caused by the alignment of magnetic moments and induced magnetism is created when disordered magnetic moments are forced to align in an applied magnetic field. For example, the ordered magnetic moments ( ferromagnetic, Figure 1) change and become disordered ( paramagnetic, Figure 2) at the Curie temperature. Higher temperatures make magnets weaker, as spontaneous magnetism only occurs below the Curie temperature. Magnetic susceptibility above the Curie Temperature can be calculated from the Curie–Weiss law, which is derived from Curie's law.

In analogy to ferromagnetic and paramagnetic materials, the Curie temperature can also be used to describe the phase transition between ferroelectricity and paraelectricity. In this context, the order parameter is the electric polarisation that goes from a finite value to zero when the temperature is increased above the Curie temperature.

Curie temperature of materials

Material

Curie
temperature (K)

Iron (Fe)

1043

Cobalt (Co)

1400

Nickel (Ni)

627

Gadolinium (Gd)

292

Dysprosium (Dy)

| 88

Mn Bi

| 630

Mn Sb

| 587

CrO

| 386

Mn As

| 318

EuO

| 69

Iron(III) oxide (FeO)

948

Iron(II,III) oxide (FeOFeO)

| 858

NiOFeO

| 858

CuOFeO

| 728

MgOFeO

| 713

MnOFeO

| 573

YFeO

| 560

Neodymium magnets

|

Alnico

|

Samarium–cobalt magnets

|

Strontium ferrite

|