Researchers have found a trick that could make writing data to a hard disk as much as a thousand times faster. Recording information in today’s magnetic memory and magneto-optical drives uses an external magnetic field and/or a laser that heats up tiny spots, one at a time, to the point where the magnetic field can switch the magnetic ordering, to store single binary digits. The speed of the magnetic switching is limited by how long it takes the laser to heat the spot close to its Curie point and the external field to reverse the magnetic region. With this approach it is extremely difficult, if not impossible, to push data transfer rates beyond the gigahertz range (109 cycles per second). In the new technique, short laser pulses, interact with so-called colossal magnetoresistive materials to create ultra-fast changes in the magnetic structure, from anti-ferromagnetic to ferromagnetic ordering — anti-parallel to parallel magnetic alignment associated with huge magnetization change. These materials are highly responsive to the external magnetic fields used to write data into memory, but do not require heat, to trigger magnetic switching. The newly discovered mechanism switches magnetic ordering much faster and potentially opens the door to terahertz (1012 hertz) memory speeds.
Femtosecond Switching of Magnetism via Strongly Correlated Spin-Charge Quantum Excitations