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Excited magnetization dynamics in a spin-valve device consisting of an in-plane polarizer and an out-of-plane free layer were studied numerically. In the case where the free layer is assumed to lack any in-plane anisotropy components, a finite external field is required to generate steady-state dynamics, in agreement with previous reports. We demonstrate that this constraint can be removed and precession can be stabilized in zero applied field by introducing an additional in-plane anisotropy axis. Moreover, the in-plane anisotropy offers an additional degree of freedom for tuning the frequency response of the device.

We use a focused helium ion beam microscope to controllably remove material from Pt-capped Co/Pt thin film multilayers with perpendicular magnetic anisotropy. The dose required to remove several nm of the cap layer is similar to that required to induce a spin reorientation transition. Milling depth for the Pt overlayer is found to scale with the logarithm of ion dose, with very high removal yields of hundreds of atoms per He+ ion at low doses. While the deposited energy is of order of previous broad beam helium irradiations, the current density impacting on the surface of the sample is several tens of A cm−2, orders of magnitude higher. Patterning of the platinum capping layer with 20 nm resolution is demonstrated.

Data are presented which indicate a modification of magnetic anisotropy in the MgO/CoFeB/Pd and MgO/CoFeB/Pt systems, using electric fields of order 500 MV m−1 (0.5 V nm−1) applied across a thermally grown SiO2 as a gate dielectric. The effect is most prominent at low temperature (12 K) and is manifested as a small change in coercivity. The sign of the effect depends on the choice of both capping layer and annealing temperature. The results suggest that both interfaces play a role in the appearance of perpendicular magnetic anisotropy in these thin-film stacks, and not just the interface with MgO.

A dual spin valve is built with exchange bias on the top and bottom pinned layers and a central free layer. By suitable choice of the antiferromagnetic and ferromagnetic layer thicknesses, it is possible to separate the three magnetization switching fields and produce a staircase magnetoresistive curve. The maximum magnetoresistance (MR) ratio is 7.6% for current-perpendicular-to-plane and 6.3% for current-in-plane geometries with intermediate MRs of 3.9% and 3.0%, respectively. The use of exchange bias in a multistate memory device is discussed.