High spin polarization in the ferromagnetic filled skutterudites KFe4Sb12 and NaFe4Sb12

TL;DR

This study measures high intrinsic spin polarization in ferromagnetic KFe4Sb12 and NaFe4Sb12 using point-contact Andreev reflection, confirming their potential as highly spin-polarized ferromagnets with theoretical support.

Contribution

It provides experimental evidence of high spin polarization in these filled skutterudites, aligning with band structure calculations, and highlights their potential for spintronic applications.

Findings

KFe4Sb12 has 67% spin polarization

NaFe4Sb12 has 60% spin polarization

Results agree with LSDA band structure predictions

Abstract

The spin polarization of ferromagnetic alkali-metal iron antimonides KFe4Sb12 and NaFe4Sb12 is studied by point-contact Andreev reflection using superconducting Nb and Pb tips. From these measurements an intrinsic transport spin polarization Pt of 67% and 60% for the K and Na compound, respectively, is inferred which establishes these materials as a new class of highly spin polarized ferromagnets. The results are in accord with band structure calculations within the local spin density approximation (LSDA) that predict nearly 100% spin polarization in the density of states. We discuss the impact of calculated Fermi velocities and spin fluctuations on Pt.