On conservation of the of crystal lattice symmetry in transition at Curie point in exchange magnets

TL;DR

This paper investigates how the crystal lattice and magnetic symmetries of exchange and non-exchange magnets change at the Curie point, revealing that exchange magnets preserve lattice symmetry while non-exchange magnets do not.

Contribution

It demonstrates that crystal lattice symmetry remains unchanged at the Curie point in exchange magnets, contrasting with non-exchange magnets where both magnetic and chemical symmetries decrease.

Findings

Exchange magnets retain lattice symmetry at Curie point.

Non-exchange magnets lose both magnetic and chemical symmetry at Curie point.

Magnetic symmetry in exchange magnets is described by P-type color groups.

Abstract

We show that symmetry of the crystal lattice of exchange magnets (containing only 3d magneto-active elements) does not change at the Curie point; only the magnetic symmetry of the crystal is decreasing in the transition point. In the non-exchange magnets (containing only rare-earth magneto-active elements), on the contrary, both the magnetic and crystal-chemical symmetry decrease at the Curie point. There is isotropic magnetic phase in exchange magnets; and their magnetic symmetry is described by color groups of magnetic symmetry of P-type. Non-exchange magnets do not have isotropic phase; their symmetry is described by color groups of magnetic symmetry of Q-type.