Depth dependent spin dynamics of canonical spin glass films: A low-energy muon spin rotation study

TL;DR

This study investigates how spin dynamics in thin spin glass films vary with depth and thickness using muon spin rotation, revealing increased impurity spin activity near surfaces and in thinner samples.

Contribution

It provides the first detailed depth-dependent analysis of spin dynamics in canonical spin glass films using low-energy muon spin rotation.

Findings

Increased impurity spin dynamics near the surface of spin glass films.

Reduced relaxation rates in thinner films indicating incomplete spin freezing.

Surface effects influence spin behavior without significantly changing freezing temperature.

Abstract

We have performed depth dependent muon spin rotation/relaxation studies of the dynamics of single layer films of {\it Au}Fe and {\it Cu}Mn spin glasses as a function of thickness and of its behavior as a function of distance from the vacuum interface (5-70 nm). A significant reduction in the muon spin relaxation rate as a function of temperature with respect to the bulk material is observed when the muons are stopped near (5-10 nm) the surface of the sample. A similar reduction is observed for the whole sample if the thickness is reduced to e.g. 20 nm and less. This reflects an increased impurity spin dynamics (incomplete freezing) close to the surface although the freezing temperature is only modestly affected by the dimensional reduction.