Measured Relaxation Times for the Uniaxial-Anisotropy Spectrum in Nonmagnetostrictive Permalloy Films

Abstract

The relaxation time τ for realignment of an atomic anisotropy by 90° has been measured for a number of fast processes (τ<103 sec) occurring in nonmagnetostrictive Permalloy films. The method of measurement utilizes the magnetoresistance effect and is described in detail elsewhere. For films deposited between 23° and 200°C at 10−6 to 10−5 Torr and measured at the same temperature and pressure, three distinct processes plus two probable ones have been found, which together account for about one-quarter of the total anisotropy. The activation energy Q and period factor τ0 which determine the relaxation time τ=τ0 exp (Q/kT) have been determined for each of these processes.

Switching field interval of the sensitive magnetic layer in exchange-biased spin valves

“…This study was motivated by reports that the induced anisotropy of thin films may change upon annealing in a magnetic field, even at temperatures in the order of 100-200°C. [17][18][19][20] Indeed, we observed that ⌬H s may change dramatically when the spin valves are subjected to elevated temperatures. This is relevant from an applications point of view, since process steps at a temperature of 150-200°C are very common in the fabrication of magnetoresistive sensing devices.…”

“…In Fig. 5, the 18 Co 12 -layer thickness. So the increase in coupling strength with increasing thickness of the sensitive layer is entirely ascribed to the evolution of the lateral length scale of the roughness.…”

“…1,2 Ni 80 Fe 20 ͑permalloy͒ is sometimes replaced by a Ni-Fe-Co ͑Ref. 3͒ or Co-Fe alloy, 4,5 preferably close to a composition such as Ni 66 Fe 16 Co 18 for which the magnetostriction is nearly zero. 6 Especially spin valves with crossed anisotropies of the sensitive and exchange-biased magnetic layers are very favorable for applications, because they exhibit a high sensitivity combined with an extremely low coercivity.…”