A study of muon localization and diffusion in Hf₂Co and Hf₂CoH₃

Abstract

AbrlracL Muon spin relaxation (0s) aperimenu were mrried out in zero field on polycrystalline samples of Hf2Co and HfiCoHs. In lhe unhydrided alloy the muon preferentially oacupies Octahedral intess1iee-s and diEuses through a tunnelling mechanism within lhe network made oi adjacent octahedra above PO K In mnlrast, the muon -pies lelrahedral inlemtices in the hydrided alloy. Muon diffusion takes place through two distinct phonon-assisted tunnelling mechanisms wilh a possible contribution of overbarrier hopping above 250 & and appears lo be slrongly enhaneed by the presence of hydrogen. This eEed b attribuled U) the different pathways taken bj the muon in hydrided and unhydrided Hf2Co. A comparison with llie hydrogen jump rate measured by pwlurbed angular correlation in the same hydride provides confirmation that the hydrogen mobility is indeed faster than that of the muon, which appears lo be a quite general result in concentrated metallic hydrides.

Arrhenius Jump Rate of Muons in Some Non-Stoichiometric Metallic and Intermetallic Hydrides

“…Muon diffusion in this hydride is qualitatively similar to that observed in Zr2NiH4 [22]. The muon becomes localized at interstitial sites at low temperatures up to 100 K above which the muon can diffuse in a tunnelling process.…”

“…Over the temperature range 100-250 K the-jump rate for muon diffusion is given by Above 250 K muon diffusion and hydrogen diffusion become identical governed by the same activation energy Pe. 240 meV [22]. Muon diffusion may be considered as an over-barrier hopping process with a rate…”

Arrhenius Jump Rate of Muons in Metals and Metallic Compounds

“…Diffusion of muon in highly pure Hf2Co was studied up to room temperature by Baudry et al [15]. Muons were found to be localized at different interstitial positions below 200 K over which the muons diffuse in a tunnelling process.…”

“…Muon diffusion in this high temperature superconducting alloy has been studied over 2-350 K [15]. In this alloy muon is found to be localized below 200 K.…”

Ab-initio studies of thermal and superconducting properties of HfX2 alloys (X = Tc, Re, and Os)

“…Several are hexagonal C14 Laves structure alloys. Some intermetallic compounds of Hf and the transition metals Fe, Co, Pd and Pt have been investigated as hydrogen-storage materials because of their capability to form hydrides with high hydrogen to metal ratios at room temperature [3]. Hafnium is primarily used in the control and safety mechanisms of nuclear reactors because of its high cross-section for neutron absorption and its high corrosion resistance [4].…”