Spin dynamics of S-state ions in the filled skutterudites La1-xRx$Pt4Ge12 (R= Gd, Eu)

TL;DR

This study investigates the spin dynamics of Gd3+ and Eu2+ ions in filled skutterudites using ESR, revealing vibrational behavior of Gd3+ ions and highlighting the significance of rattling modes in cage systems.

Contribution

It provides direct ESR evidence of vibrational behavior and an extra phonon mode in Gd3+ ions within skutterudites, emphasizing the role of rattling modes in spin relaxation.

Findings

Gd3+ ions exhibit vibrational behavior detectable by ESR.

An extra phonon mode with thetaE ~ 24 K is identified in Gd-doped skutterudites.

Rattling modes significantly influence spin dynamics in cage systems.

Abstract

A detailed study of the spin dynamics of the S-state ions Gd3+ and Eu2+ in the filled skutterudites La1-xRxPt4Ge12 (R= Gd, Eu) is reported. The spin dynamics is investigated directly by means of Gd3+ and Eu2+ electron spin resonance (ESR), performed at X-band (~ 9.4 GHz) and Q-band (~ 34 GHz) frequencies in the temperature intervals 8<T<300 K and 1.5<T<300 K respectively. The ESR parameters provide direct evidence for the vibrational behavior of the Gd3+ ions but not for the Eu2+ ions. These results are interpreted in the light of recent discussions about the spin relaxation in cage systems. In particular, the Gd3+ spin relaxation in La0.9Gd0.1Pt4Ge12 provide evidence for the existence of an extra phonon mode with an Einstein temperature (thetaE) ~ 24 K in this system. The work suggests that the so-called "rattling" modes have a general and important role that should be taken into account in the study of spin dynamics in cage systems.