Au quantum dots engineered room temperature crystallization and magnetic anisotropy in CoFe 2 O 4 thin films

Sagar E. Shirsath, Xiaoxi Liu, M. H.N. Assadi, Adnan Younis, Yukiko Yasukawa, Sumanta Kumar Karan, Ji Zhang, Jeonghun Kim, Danyang Wang, Akimitsu Morisako, Yusuke Yamauchi, Sean Li

Research output: Contribution to journalArticlepeer-review

88 Citations (Scopus)


For the first time, this work presents a novel room temperature time-effective concept to manipulate the crystallization kinetics and magnetic responses of thin films grown on amorphous substrates. Conventionally, metal-induced crystallization is adopted to minimize the crystallization temperature of the upper-layer thin film. However, due to the limited surface area of the continuous metal under-layer, the degree of crystallization is insufficient and post-annealing is required. To expose a large surface area of the metal under-layer, we propose a simple and novel approach of using an Au nanodots array instead of a continuous metallic under-layer to obtain crystallization of upper-layer thin films. Spinel cobalt ferrite (CFO) thin film as a 'model' was deposited on an Au nano-dots array to realize this methodology. Our findings revealed that the addition of quantum-sized Au nano-dots as a metal under-layer dramatically enhanced the crystallization of the cobalt ferrite upper layer at room temperature. The appearance of major X-ray diffraction peaks with high intensity and well-defined crystallized lattice planes observed via transmission electron microscopy confirmed the crystallization of the CFO thin film deposited at room temperature on 4 nm-sized Au nano-dots. This crystallized CFO thin film exhibits 18-fold higher coercivity (H c = 4150 Oe) and 4-fold higher saturation magnetization (M s = 262 emu cm -3 ) compared to CFO deposited without the Au under-layer. The development of this novel concept of room-temperature crystallization without the aid of additives and solvents represents a crucial breakthrough that is highly significant for exploring the green and energy-efficient synthesis of a variety of oxide and metal thin films.

Original languageEnglish
Pages (from-to)516-525
Number of pages10
JournalNanoscale Horizons
Issue number2
Publication statusPublished - Mar 2019
Externally publishedYes

ASJC Scopus subject areas

  • General Materials Science


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