Long lived excitations in fully compensated antiferromagnetic nanomagnets*

Extensive interest is directed towards finding long lived states in atomic scale magnetic structures. Applications include classical and quantum spintronics schemes. Here we use a recently described method of applying a single atom exchange bias, using a magnetic scanning tunneling microscope tip [1], to control the quantum states of fully compensated nano-antiferromagnetic atomic chains. We apply time-resolved spin-polarized scanning tunneling microscopy to measure the energy relaxation of the chains as a function of the tip interaction strength. With strong coupling to the microscope tip, the excited state lifetimes can extend to the millisecond scale. [1] Nature Nanotech. 10, 40 (2015).