Bias-free tunability of microwave properties in multilayer rhomboid shaped nanomagnets.

The magnetization dynamics of single multilayer rhomboid shaped nanomagnets is investigated using micro-focused Brillouin light scattering spectroscopy. The nanomagnets consist of two permalloy layers separated by a nonmagnetic Cr spacer layer. By varying the Cr thickness in the range from 0 to 15 nm, the dipolar coupling is effectively controlled, thus modifying the corresponding magnetic ground states. The magnetization dynamics as a function of initialization field orientation has been systematically investigated. A significant tunable frequency difference of ~2 GHz in the microwave absorption between ferromagnetic and antiferromagnetic ground states is observed as the size of nanomagnets is varied. Micromagnetic simulations validate our experimental observations. [ABSTRACT FROM AUTHOR]