Paramagnets

Paramagnet in the absence of a magnetic field .

Paramagnet in the presence of a strong magnetic field.

Paramagnets are substances that are magnetized in an external magnetic field in the direction of an external magnetic field ( J ↑↑ H ) and have a positive magnetic susceptibility , but significantly less than unity. Paramagnets belong to strongly magnetic substances, magnetic permeability differs slightly from unity${\displaystyle \mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">\mu </span></span>}<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">\gtrsim </span></span>\mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">one</span></span>}}$ {\ displaystyle \ mu \ gtrsim 1} .

The term “Paramagnetism” was introduced in 1848 by Michael Faraday , who divided all substances into ferromagnetic , diamagnetic , paramagnetic, speromagnetic (asperomagnets) and ferrimagnetic (micromagnets).

The substances of the paramagnet have their own magnetic moments , which, under the action of external fields, are oriented along the field and thereby create a resulting field that exceeds the external one. Paramagnets are drawn into a magnetic field. In the absence of an external magnetic field, the paramagnet is not magnetized, since due to thermal motion the intrinsic magnetic moments of atoms are oriented completely randomly.

Paramagnets include aluminum (${\displaystyle \text{<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;">Al</span></span>}}$ {\ displaystyle {{\ ce {Al}}}} ), platinum (${\displaystyle \text{<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;">Pt</span></span>}}$ {\ displaystyle {{\ ce {Pt}}}} ), many other metals (alkali and alkaline earth metals, as well as alloys of these metals), oxygen (${\displaystyle {\text{<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;">O</span></span>}}_{\mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">2</span></span>}}^{}}$ {\ displaystyle {\ ce {O2}}} ), nitric oxide (${\displaystyle \text{<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;">NO</span></span>}}$ {\ displaystyle {{\ ce {NO}}}} ), manganese oxide (${\displaystyle \text{<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;">MnO</span></span>}}$ {\ displaystyle {{\ ce {MnO}}}} ), ferric chloride (${\displaystyle {\text{<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;">FeCl</span></span>}}_{\mathrm{<span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">3</span></span>}}^{}}$ {\ displaystyle {\ ce {FeCl3}}} ) other.

Ferro- and antiferromagnetic substances become paramagnets at temperatures exceeding, respectively, the Curie or Néel temperature (temperature of the phase transition to the paramagnetic state).

Properties:

- The magnetic susceptibility of paramagnets is positive and significantly less than unity.

- At not too high temperatures, paramagnets have spontaneous magnetization, which varies greatly under the influence of external influences.

- For paramagnets, the phenomenon of hysteresis is characteristic.

- Paramagnets are attracted by a magnet in the presence of a strong magnetic field, but in the absence they are not attracted.