# Magnon Condensation and Spin Superfluidity

## TL;DR

This paper explores magnon Bose-Einstein condensation and spin superfluidity, highlighting their occurrence beyond classical models and estimating critical conditions in various magnetic materials.

## Contribution

It introduces the concept of magnon BEC and spin superfluidity beyond classical paradigms, with specific estimates for different magnetic systems.

## Key findings

- BEC occurs at lower magnon densities in hematite than in YIG.
- Critical conditions for magnon condensation are estimated for ferro- and antiferromagnets.
- Magnon BEC and spin superfluidity are demonstrated beyond classical models.

## Abstract

We consider the phenomenon of Bose-Einstein condensation of quasi-equilibrium magnons which leads to a spin superfluidity, the coherent quantum transfer of magnetization in magnetic materials. These phenomena are beyond the classical Landau-Lifshitz-Gilbert paradigm. The critical conditions for excited magnon density for ferro- and antiferromagnets, bulk and thin films are estimated and discussed. The BEC should occur in the antiferromagnetic hematite at much lower excited magnon density compared to the ferromagnetic YIG.