Improved magnetization in sputtered dysprosium thin films

TL;DR

This study reports enhanced magnetization in sputtered dysprosium thin films, achieving near-single crystal magnetic properties through optimized deposition conditions, with detailed analysis of phase and strain effects.

Contribution

It introduces a method to produce dysprosium thin films with improved magnetization and elucidates the effects of crystal phase and strain on magnetic properties.

Findings

Maximum in-plane magnetization of 3.28T at 4K on heated substrates

Ferromagnetic transition temperature of 80K in optimized films

Reduced magnetization in as-deposited films with higher transition temperature

Abstract

50nm thick nanogranular polycrystalline dysprosium thin films have been prepared via ultra-high vacuum DC sputtering on SiO2 and Si wafers. The maximum in-plane spontaneous magnetization at T = 4K was found to be MS4K = 3.28T for samples deposited on wafers heated to 350C with a Neel point of TN = 173K and a ferromagnetic transition at TC = 80K, measured via zero field cooled field cooled magnetization measurements, close to single crystal values. The slightly reduced magnetization is explained in the light of a metastable face centered cubic crystal phase which occurred at the seed interface and granularity related effects, that are still noticeably influential despite an in-plane magnetic easy axis. As deposited samples showed reduced magnetization of MS4K = 2.26T, however their ferromagnetic transition shifted to a much higher temperature of TC = 172K and the antiferromagnetic phase was completely suppressed probably as a result of strain.