Scanning Thermal Microscopy and Ballistic Phonon Transport in Lateral Spin Valves

Area of Science:

• Condensed Matter Physics
• Nanotechnology
• Materials Science

Background:

• Understanding thermal transport at the nanoscale is crucial for designing efficient electronic devices.
• Previous studies have focused on diffusive heat transport, with less attention paid to low-temperature phenomena.

Purpose of the Study:

• To spatially map temperature distributions in an operating nanoscale magnetic device.
• To investigate thermal diffusion mechanisms at temperatures down to 2 K.
• To analyze the influence of ballistic phonon transport on heat diffusion.

Main Methods:

• Scanning thermal microscopy (SThM) was employed to measure temperature distributions.
• An analytical model was developed to describe thermal diffusion.
• Experiments were conducted on a device comprising a magnetic injector, silver connecting wire, and magnetic detector.

Main Results:

• Spatial temperature distributions were successfully mapped in the nanoscale device.
• Thermal diffusion was modeled across a temperature range of 2–300 K and separations of 400–3000 nm.
• A remarkable difference in characteristic diffusion lengths for Peltier and Joule heat was observed below 60 K.

Conclusions:

• The observed differences in heat diffusion lengths below 60 K are attributed to the onset of ballistic phonon heat transfer.
• This finding highlights the importance of considering ballistic transport in nanoscale thermal management at low temperatures.
• The study provides insights into the fundamental thermal properties of nanomaterials and devices.