Influence of thermal excitation on magnetization states and switching routes of magnetic multilayer rings.

The low temperature magnetic switching behavior of micron scale NiFe/Cu/Co circular ring elements has been investigated using micromagnetic simulations and magnetoresistance (MR) measurements. The rings were patterned, so that two different contact configurations could be used to measure MR simultaneously. By comparing these measurements with the simulation results, the rings’ magnetization states and switching routes were determined at both 1.7 and 300 K. It was found that at 1.7 K the rings exhibited multiple switching routes and also showed more metastable states and broader transitions between states than was observed at 300 K. The rings’ behavior at low temperature is explained as the result of an increase in the strength of magnetocrystalline and magnetoelastic anisotropies combined with an absence of thermal excitation which would usually aid the nucleation and depinning of domain walls. [ABSTRACT FROM AUTHOR]