Understanding the mechanism of ferromagnetism in the semiconductor (Ga,Mn)As

Ferromagnetic semiconductors are functional materials pivotal to the development of spintronics, which are poised to be the next generation of information processing. However, the range of operational temperature remains a practical challenge for the technology, as spin-dependent phenomena can only occur below the Curie temperature of a material. To better understand the mechanism of ferromagnetism for realizing room-temperature spintronics devices, Takeda et al. studied the onset of ferromagnetic ordering in manganese-doped gallium arsenide.

Among the three samples studied, the researchers were able to identify several common behaviors in the magnetic ordering process, despite the samples having different Curie temperatures, manganese concentrations and electrical resistivities. When a magnetic field is applied around the Curie temperature of the material, some of the gallium sites are replaced by manganese ions. The electronic states surrounding the manganese ions, which substitute parts of the gallium site, trigger the onset of ferromagnetic ordering around the Curie temperature of the materials.

By investigating a wide range of applied temperatures and fields, the researchers studied how the conditions of the semiconductor (Ga,Mn)As films affect their magnetic properties and ordering. They used soft X-ray magnetic circular dichroism experiments to monitor these effects.

According to the authors, because ferromagnetic semiconductors can directly follow many of the same applications as more mature semiconductor technologies, it should not take long to achieve advances in practical spintronics devices once room-temperature ferromagnetism is realized.

“Once room-temperature ferromagnetic semiconductors are realized, perhaps there is a high possibility that practical devices would come up immediately, leading to the next generation of information technology,” said author Yukiharu Takeda.

Source: “Direct observation of the magnetic ordering process in the ferromagnetic semiconductor Ga_1-xMn_xAs via soft x-ray magnetic circular dichroism,” by Yukiharu Takeda, Shinobu Ohya, Pham Nam Hai, Masaki Kobayashi, Yuji Saitoh, Hiroshi Yamagami, Masaaki Tanaka, and Atsushi Fujimori, Journal of Applied Physics (2020). The article can be accessed at https://doi.org/10.1063/5.0031605 .