A research team led by Prof. SHENG Zhigao from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has manipulated the structure and microwave absorption of Co_xSe nanosheets by synthesizing them under a high magnetic field (HMF). The material's reflection loss improved dramatically from −6.3 dB at 0 T to −66.3 dB at 10 T in the C-band (4–8 GHz), representing more than a tenfold improvement.

The findings were published in Chemical Engineering Journal on February 11.

Microwave-absorbing materials are essential for reducing electromagnetic interference in radar and wireless communication systems. As electronic devices continuously emit electromagnetic waves, effective absorption in the C-band frequency range is increasingly important for improving signal stability and minimizing interference.

The researchers conducted a systematic investigation of the magneto-synthetic control of heterophase Co_xSe nanosheets under an HMF using a magneto-solvothermal setup, which consists of a superconducting magnet, a heating reactor, and a water chiller. This setup enabled the formation of the material under precisely controlled HMF conditions, providing a new level of control beyond traditional synthesis parameters, such as temperature and pressure.

Under HMF conditions, the composition of Co_xSe was modulated to form heterophase Co_0.85Se/Co_0.5Se nanosheets with anisotropic growth. Simultaneously, the material underwent a magnetic transition from paramagnetic to ferromagnetic behavior, demonstrating that the magnetic field influenced not only its structure but also its magnetic properties.

This study shows that HMF can effectively tune materials during synthesis. By introducing this extreme condition, researchers are able to control both the structure and performance at the same time, and even obtain material phases that are difficult to achieve under conventional conditions.

"This magneto-synthesis approach offers a novel strategy for manipulating material growth and designing advanced functional materials in broad applications," said Dr. Khalifa, a member of the team.

Synthesis of heterophase Co_xSe nanosheets under high magnetic field: Modulation of composition, morphology, magnetism, and microwave absorption (Image by Khalifa)