Thermal Conductivity of a Nanoscale Yttrium Iron Garnet Thin-Film Prepared by the Sol-Gel Process.

Yun Kim

doi:10.3390/nano7090247

Abstract

The thermal conductivity of a nanoscale yttrium iron garnet (Y3Fe5O12, YIG) thin-film prepared by a sol-gel method was evaluated using the ultrafast pump-probe technique in the present study. The thermoreflectance change on the surface of a 250 nm thick YIG film, induced by the irradiation of femtosecond laser pulses, was measured, and curve fitting of a numerical solution for the transient heat conduction equation to the experimental data was performed using the finite difference method in order to extract the thermal property. Results show that the film’s thermal conductivity is 22–83% higher than the properties of bulk YIG materials prepared by different fabrication techniques, reflecting the microstructural characteristics and quality of the film.

Highlights

Yttrium iron garnet (Y3Fe5O12, YIG) is a ferrimagnetic material that is promising for applications in microwave communication systems and magneto-optic devices because of its distinctive magnetic and structural properties such as the narrow linewidth of the ferromagnetic resonance, low magnetic loss, and moderate saturation magnetization [1]
With the evolution of microfabrication techniques, novel thin-film based magnetic sensors and data storage media are developed, and the fabrication and characterization of nanoscale YIG films have become important research topics since their properties are often different from those of the bulk form and the device performance is strongly influenced by fabrication techniques that determine the film quality and microstructures [2]
The ultrafast pump-probe technique was employed for the measurement because it is especially effective for nanoscale materials characterization, providing non-contact and nondestructive ways to measure thermal properties with high temporal and spatial resolutions [18]

Summary

Introduction

Yttrium iron garnet (Y3Fe5O12, YIG) is a ferrimagnetic material that is promising for applications in microwave communication systems and magneto-optic devices because of its distinctive magnetic and structural properties such as the narrow linewidth of the ferromagnetic resonance, low magnetic loss, and moderate saturation magnetization [1]. The sol-gel method is mainly advantageous in that it is cost-effective [9] It can produce films of high purity and homogeneity at lower synthesis temperature [10,11,12,13]. The ultrafast pump-probe technique was employed for the measurement because it is especially effective for nanoscale materials characterization, providing non-contact and nondestructive ways to measure thermal properties with high temporal and spatial resolutions [18]. It can measure the thermal conductivity and thermal boundary conductance of a very thin film of which thickness is only a few tens of nanometers. Unlike the 3ω method [21], in situ testing is possible because it does not require physical contact for the measurement, and electrically conducting materials can be measured since it is an optical technique, without the need for patterning metallic strip heaters on the sample surface

Sample Preparation

Ultrafast Pump-Probe Technique

Results and Discussion

Conclusions