Physicists at MIT have directly stimulated atoms in an antiferromagnetic material using a terahertz laser, a light source that oscillates more than a trillion times per second.
Their results provide a new way to control and switch antiferromagnetic materials, which are of interest for their potential to advance information processing and memory chip technology. In common magnets, known as ferromagnets, the spins of atoms point in the same direction, in a way that the whole can be easily influenced and pulled in the direction of any external magnetic field. In contrast, antiferromagnets are composed of atoms with alternating spins, each pointing in the opposite direction from its neighbor. This up, down, up, down order essentially cancels the spins out, giving antiferromagnets a net zero magnetization that is impervious to any magnetic pull. If a memory chip could be made from antiferromagnetic material, data could be 'written' into microscopic regions of the material, called domains. A certain configuration of spin orientations (for example, up-down) in a given domain would represent the classical bit '0,' and a different configuration (down-up) would mean '1.' Data written on such a chip would be robust against outside magnetic influence. For this and other reasons, scientists believe antiferromagnetic materials could be a more robust alternative to existing magnetic-based storage technologies. A major hurdle, however, has been in how to control antiferromagnets in a way that reliably switches the material from one magnetic state to another. Using carefully tuned terahertz light, MIT Professor Nuh Gedik and colleagues were able to controllably switch an antiferromagnet to a new magnetic state. "Antiferromagnetic materials are robust and not influenced by unwanted stray…