Curie-Weiss law

The Curie-Weiss law (according to Pierre Curie and Pierre-Ernest Weiss ) describes the magnetic properties of ferromagnetic substances in which magnetic cooperative effects lead to a deviation from the ideal Curie behavior . Such cooperative effects occur due to the exchange interaction, the direct interaction of magnetic dipole moments of neighboring paramagnetic atoms plays a subordinate role. This influence leads to ferromagnetism below the Curie temperature . ${\displaystyle \chi _{m}={\tfrac {C}{T}}}$

The Curie-Weiss law shows the temperature dependence of the magnetic susceptibility of a ferromagnet in the high temperature phase, i.e. H. above the Curie temperature ${\displaystyle \chi _{m}}$ ${\displaystyle T_{c}:}$

${\displaystyle \chi _{m}={\frac {C}{T-T_{c}}}}$

with the Curie constant . ${\displaystyle C}$

The equation states that the magnetic susceptibility in the paraphase diverges as the temperature approaches the Curie temperature from above . ${\displaystyle T}$

Analogue for ferromagnetic and antiferromagnetic systems

In ferromagnetic and antiferromagnetic systems, the magnetic susceptibility above their phase transition temperature , the Néel temperature , can be described by a slightly modified formula: ${\displaystyle T_{N},}$

${\displaystyle \chi _{m}={\frac {C}{T+T_{N}}}.}$

In this case, the susceptibility of the high-temperature phase apparently “diverges” towards a negative temperature.

literature

• Heiko Lueken : Magnetochemistry . BG Teubner, Stuttgart / Leipzig 1999, ISBN 3-519-03530-8 .
• Bergmann-Schaefer Textbook of Experimental Physics Volume 2: Electricity and Magnetism 7th edition, de Gruyter, 1987, ISBN 3-11-010261-7

Individual evidence

1. ^ Entry on Curie-Weiss law. In: Römpp Online . Georg Thieme Verlag, accessed on July 24, 2016.