# The Effect of Magnetic Impurities on Superfluid $^3$He in Aerogel

## TL;DR

This paper investigates how magnetic impurities in anisotropic silica aerogel influence the stability of superfluid $^3$He phases, revealing that magnetic impurities suppress the $A$ phase more than the $B$ phase, affecting the critical field.

## Contribution

It demonstrates that magnetic impurities in anisotropic aerogel selectively suppress the $A$ phase, providing insight into impurity effects on superfluid phases and their symmetry properties.

## Key findings

- Magnetic impurities suppress the $A$ phase relative to the $B$ phase.
- The symmetry of $A$ and $B$ phases remains unchanged in anisotropic aerogel without magnetic scattering.
- Results have implications for understanding unconventional superconductivity.

## Abstract

The critical field for superfluid $^3$He in axially compressed, anisotropic silica aerogel is shown to be the result of an anisotropic distribution of magnetic impurities affecting the superfluid $A$ phase. The critical field results from the fact that the $A$ phase is suppressed relative to the $B$ phase which is immune to the effects of magnetic impurities. In the absence of magnetic quasiparticle scattering in anisotropic aerogel, we find that the relative symmetry of $A$ and $B$ phase order parameters is the same as in isotropic aerogel, just as it is in pure superfluid $^3$He. These results are of potential importance for understanding unconventional superconductivity.