Influence of demagnetization in remanence curves of magnetic thin films
Remanent magnetization curves of perpendicular magnetic thin films are simulated and measured. The simulations are used to investigate the theoretical influence of the strong demagnetizing field present in these films. Conclusions are drawn from this on how remanence curves should be measured and how they should be corrected for the demagnetizing influence. The experimental part consists of measurements on Fe‐Alumite, Co‐Pt–based multilayers, and Co‐Cr. In addition the latter material is also artificially patterned into microstrips in order to investigate the influence of demagnetization on remanence curves experimentally.
Self consistent measurement and removal of the dipolar interaction field in magnetic particle assemblies and the determination of their intrinsic switching field distribution
Using low density arrays of bistable magnetic nanowires as a model dipolar system, it is shown that the dipolar interaction field coefficient can be measured from the remanence curves as well as from other functions of the isothermal remanent magnetization and the DC demagnetization remanence obtained as an affine transformation of the Wohlfarth relation. Based on mean field arguments, these measurements are used to subtract and remove the contribution of the configuration dependent dipolar interaction field from the major loop and remanence curves. The corrected remanence curves are first used to obtain the intrinsic switching field distribution of the nanowire array and then to validate this approach showing that they yield results consistent with the Wohlfarth relation for an assembly of noninteracting particles, thus providing a self-consistent procedure to verify the measured values of the interaction field and its removal from the measurements.
Magnetization decay in Co‐Cr films
We have measured magnetization time decay in perpendicularly oriented Co‐Cr films over seven time decades as a function of field and temperature. The anomalous Hall coefficient of the sample itself, which is proportional to the magnetization within the sample, is used to determine the magnetization. Magnetization time decay measurements made with this technique, for times>10 s, agree with vibrating‐sample magnometer (VSM) data taken at 77 and 300 K, but can be made as soon as 2 ms after turning off the external magnetic field used to saturate the sample. The principle features of magnetization decay in Co‐Cr are as follows: (1) The magnetization time decay in Co‐Cr films is nearly independent of external field over a range of several kG, unlike particulate media, where the magnetization decay rate is sharply peaked around the coercive field. (2) At 300 K, the magnetization time decay deviates markedly from log t, with the decay per decade of time dropping by almost a factor of 2 between 10−3 and 104 s. (3...