Ferromagnetism in Fe-doped Ba6Ge25 Chiral Clathrate

TL;DR

This study reports the synthesis of a Fe-doped Ba6Ge25 chiral clathrate exhibiting ferromagnetism with a transition temperature of 170 K, highlighting its potential as a magnetic material with disordered magnetic phases.

Contribution

First demonstration of ferromagnetism in Fe-doped Ba6Ge25 chiral clathrate with high transition temperature and analysis of its magnetic disorder.

Findings

Ferromagnetic transition at Tc = 170 K

High-spin magnetic moments in Fe atoms

Transition to a re-entrant spin glass phase

Abstract

We have successfully synthesized a Ba6Ge25 clathrate, substituting 3 Fe per formula unit by Ge. This chiral clathrate has Ge sites forming a framework of closed cages and helical tunnel networks. Fe atoms randomly occupy these sites, and exhibit high-spin magnetic moments. A ferromagnetic transition is observed with Tc = 170 K, the highest observed Tc for a magnetic clathrate. However, the magnetic phase is significantly disordered, and exhibits a transformation to a re-entrant spin glass phase. This system has a number of features in common with other dilute magnetic semiconductors.