Insight into the fast emergence of magnetization

A group of scientists have found the speed of magnetizing a material.

One of the most intriguing questions of magnetism is how fast magnets can be created.

Their work is published in a journal.

When heated just above room temperature, the common magnetic alloy of iron and rhodium shows a transition in both its structure and magnetism. FeRh does not have a net magnetization because of it's antiferromagnetic nature, but when heated just above room temperature, it becomes a ferromagnet.

FeRh goes through a transition into its ferromagnetic phase.

• the excitation of the laser pulse induces a large number of tiny magnetic domains in the material
• the magnetization of all the domains align along one particular direction
• the individual domains grow to coalesce into a large single domain where it can be said that the material has undergone a transition into its ferromagnetic phase

Knowledge of the various stages involved in inducing a well-defined magnetization with a light pulse gives the possibility of using FeRh in near future data storage technology.

FeRh can be used as a storage medium in heat-assisted magnetic recording, a technology that uses both external heat and local magnetic fields to store information with higher densities of bits.

Understanding the details of various stages of magnetization in a material helps scientists in developing ultrafast and energy efficient magnetic data storage technologies.

The research used a short artificial stimulation to quickly heat FeRh. The laser pulse raised the temperature by a few hundred degrees Celsius at a very short time.

For a long time, it has been a fascinating goal for researchers to use ultrafast heat and be able to control the magnetic phase transition in FeRh, but it has been a challenge to experiment with.

The scientists were able to overcome the challenge by using the fact that time-varying magnetization produces a time-varying electric field in a medium that should emit radiation. Sensitive information about the origin of the radiation can be found in the sample.

The researchers used a new technique. The first laser pulse is used for ultrafast heating and the second is used to generate electric field. The researchers were able to see how fast the magnetization emerged in the material by detecting this field at multiple times.

More information: G. Li et al, Ultrafast kinetics of the antiferromagnetic-ferromagnetic phase transition in FeRh, Nature Communications (2022). DOI: 10.1038/s41467-022-30591-2 Journal information: Nature Communications