New approach to identify altermagnetic materials

Magnetic materials have traditionally been classified as either ferromagnetic, such as the decorative magnets on iron refrigerator doors which are apparently always magnetic, or antiferromagnetic, such as two bar magnets placed end to end with opposite poles facing each other, canceling so that the material has no net magnetism. However, there appears to be a third class of magnetic materials exhibiting what in 2022 was called altermagnetism.

Under the microscope, magnetism comes from a collection of tiny magnets associated with electrons, called spin. In ferromagnetic materials, all electron spins point in the same direction, while in antiferromagnetic materials, electron spins are aligned in opposite directions, pointing half in one direction and half in the other, thus canceling out the magnetism net.

It is theoretically proposed that altermagnetic materials possess properties combining those of antiferromagnetic and ferromagnetic materials. One potential application of altermagnetic materials is in spintronics technology, which aims to efficiently use electron spin in electronic devices such as next-generation magnetic memories. However, identifying altermagnets has been a challenge.

An international research group led by Associate Professor Atsushi Hariki of the Graduate School of Engineering at Osaka Metropolitan University has developed a new method for identifying alter-magnets, using manganese telluride (α-MnTe ) as a test bench. The results were published in Physical Examination Letters.

Using a supercomputer, the researchers theoretically predicted a fingerprint of altermagnetism in X-ray magnetic circular dichroism (XMCD), which measures the difference in absorption between left and right circularly polarized light. Then, using the Diamond Light Source synchrotron in England, they experimentally demonstrated the XMCD spectrum for altermagnetic α-MnTe for the first time in the world.

“Our results show that XMCD is an effective method for the simple identification of altermagnetic materials,” said Professor Hariki. “In addition, this can be expected to further accelerate the application of altermagnets in spintronics.”