Comment on ''Superconducting decay length in a ferromagnetic metal''

TL;DR

This paper critiques a previous work on superconducting decay length in ferromagnetic metals, clarifying the correct solution to the linearized Eilenberger equation and highlighting the authors' earlier findings.

Contribution

It provides a correction to the previous solution of the Eilenberger equation in ferromagnetic regions, referencing the authors' earlier exact solution.

Findings

The previous solution was incorrect.

The authors' earlier exact solution is valid.

Clarification of the proper approach to the Eilenberger equation.

Abstract

In the paper " Superconducting decay length in a ferromagnetic metal" by Gusakova, Kupriyanov and Golubov [Pis'ma v ZhETF 83, 487 (2006); cond-mat/0605137], the authors claim that they solved the linearized Eilenberger equation in the ferromagnetic region of an S/F heterostructure at arbitrary mean free path. In this comment we show that the solution suggested by the authors is not correct and explain details of the exact solution found by us in an earlier work several years ago (Phys. Rev. B 64, 134506, (2001).