High frequency spin dynamics in magnetic heterostructures

Full text: Fast reversal processes in magnetic particles and arrays involve fundamental magnetic dynamic and relaxation processes. Magnetization dynamics can depend strongly on structure, and geometrical effects in nanometer scale structures can be of particular importance. Shape effects, for example, determine equilibrium ground states, strongly influence linear and nonlinear dynamics, and can introduce high frequency resonances into arrays of densely packed magnetic particles. One consequence is that switching times during reversal can be dramatically increased. These effects will be illustrated using results from numerical simulations and calculations of microwave response properties. The possibility of reversing the magnetization in dots during time scales comparable to relaxation rates is also discussed. A scheme is described whereby reversal may be achieved near the precession limit using pulsed fields, and the consequences of dot anisotropies, shape and size are examined. High frequency excitations and dynamic processes in interface exchange coupled magnets are discussed, with emphasis on exchange biased materials. The exchange bias effect is closely related to interface magnetic structure and magnetization processes in systems of ferromagnets exchange coupled to antiferromagnets It is shown how magnetization processes in the antiferromagnet can be studied through observation of dynamic effects in the ferromagnetic component