An international team of scientists has discovered the speed at which a material can be magnetized.
Researchers from Radboud University, University of California San Diego and Moscow Institute for Physics and Technology have revealed the answer to one of the most fascinating questions about magnetism: How fast is magnetization possible in a material?
Their research was published in Nature Communications.
Researchers looked at FeRh, a common magnetic alloy of iron rhodium (FeRh), which shows a transition in its structure and magnetism when heated to just above ambient temperature. FeRh is not ferromagnet at room temperature due to its antiferromagnetic nature. However, it becomes ferromagnet when heated to just above room temperature.
Researchers discovered that FeRh transitions into its ferromagnetic phase through three stages.
FeRh can be used in heat-assisted magnet recording (HAMR) as a storage medium. This technology uses both local magnetic fields and external heat to store data with a much higher density. Information is stored in tiny magnetic regions.
Dr. Rajasekhar Medapalli, a Lancaster University physicist, says that understanding the details of the rapid emergence of magnetization within a material can help scientists develop ultrafast and efficient magnetic data storage technology.
This research used intense ultrashort laser pulses to quickly heat FeRh under an artificial stimulus of only one quadrillionth. The laser pulse increased the temperature by several hundred degrees Celsius upon interaction with the material in a timescale of less than one billionth of a second.
It has been an interesting goal for condensed matter scientists to be able use the ultrafast heat to control the magnetic transition in FeRh. However, this transition has been difficult to detect experimentally.
The scientists relied on the fact that time-varying magnetic field produces a time-varying electric force in a medium that should emit radiation to overcome this challenge. The radiation that is emitted contains sensitive information about its source, namely, the time-varying magnetization of the sample.
Researchers used the Radboud University's double pump time-resolved spectrumcopy technique. Two laser pulses were used for double pumping. The first serves as an ultrafast heater and the second helps to generate an electric field. Researchers were able to detect the field at different times between the two laser pulses and see how quickly the magnetization in the material is emerging.